Here is the full message chain for those who asked (in fb).
16.1.2025 'klo' 1.43
me -> info

Hello

I got the MK4S kit a while ago and everything worked perfectly. Then all of a sudden strange problems started happening and prints started failing. I have asked for help on Reddit, but answers vary: they say it's over extruding or under extruding or that the nozzle is clogged or the usb stick is broken, and I need to use glue etc.

Especially with PLA it mostly works well, but on PETG most prints fail. There is no good adhesion despite using glue etc. or sometimes it seems like the printhead is touching the print and snapping it of from the plate. Also often while purging, the filament curls up and sometimes makes a large blob around the hot end. Sometimes it says that filament is stuck, but when I re-insert the filament it works for a while. Slowing the speed and increasing the temperature usually helps a little (on PETG), but the prints still have imperfections.

After testing many things, I figured out that the load cell values look strange. Sometimes after powering the printer, the value is -5000'ish. Then doing the load cell test, it usually goes to -30 etc. but lately completing the test is difficult. I tap the nozzle right on que, but it does not register it and I needed to repeat it 10 times. Please help me. I really love the printer and I have 10000000 print ideas, but now I do not dare to start large prints as they usually fail.

Juha

Type Original Prusa MK4S
Firmware 6.2.0-alpha2+8702
Printer UUID xxx
xBuddy SN xxx
Created 11/15/2024 3:11:30 PM

I have no invoice. I won the printer from a competition.

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16.1.2025 'klo' 13.24
Prusa support -> me

Greetings,

Thank you for your email.
Could you send us photos of the lower part of hotend from all sides when filament is loaded in extruder.
Also, could you send us photos of the prints you are having issues with.
The links from email cannot be opened, could allow public access to then so they can be seen.
Thank you.

Best regards,

—
xx
Customer Support

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16.1.2025 'klo' 13.39
me -> info

Hello

Gmail shared the files by default with info.
Now it should work with everyone. There are some images of the nozzle and some failed prints. They do not always fails the same way, but prints that earlier worked, have started to fail. At least sometimes it much feels like a Z issue, but could be something else. And possible clog/problem with nozzle could be something different or caused by the first problem or other way around. I have cleaned the nozzle and boot with brass brush, and .4mm needles and tried multiple cold pulls, but no use.

Also what I think I did not see earlier, is that when changing filament, when purge is removed, and the extruder starts moving back to position, there is always like 2 cm of filament coming out of the nozzle.. and often sticking to the print.

Juha

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16.1.2025 'klo' 15.44
Prusa support -> me

Greetings,

Thank you for your reply.
Could you send us photos of the lower part of hotend from all sides when filament is loaded in extruder. Make sure entire lower part of hotend is seen and that filament is loaded.
Also, could you send us photos of the first layer of print on the sheet and let us know what you are using to clean the sheet.
Thank you.

Best regards,

—
xx
Customer Support

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21.1.2025 'klo' 22.41 (12 päivää sitten)
-> info

Hello

Sorry for the delay. I need to find the time to do the tests and take the photos.
Juha

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22.1.2025 'klo' 14.30 (11 päivää sitten)
-> info

Hello again.
Requested images attached (sorry for focusing problems). The nozzle is a bit dirty but it prints PLA fine.
Meanwhile I did some more testing. PLA mostly works, but is very matte (even silk).
PETG mostly fails. I tried temp towers on filaments which earlier worked more or less the full range, but now they completely fail when temp goes below 250.

I did some testing with benchy. Basically. On standard settings there is no bed/layer adhesion and it just fails. 270C it worked, but has some very matte layers. 280 and 290C were very nice. No stringing or other issues which I would expect on such a high temperatures. This makes me think the root cause could be the temp sensor. Printing on too low temp would explain the repeated "filament stuck" errors. Low temp causes bad adhesion and that makes the filament come off and stick to the hot end etc.

What do you think? Is there some more info I can provide?

Juha
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23.1.2025 'klo' 13.08 (10 päivää sitten)
Prusa support -> me

Greetings,

Thank you for your reply.
Could you please let us know what you are using to clean the sheet before each print, and send us a photo of the first layer on sheet, dont remove it from the sheet.
Also, could you please send us a 3MF file of the print you are slicing.
https://help.prusa3d.com/article/saving-projects-as-3mf_1773
Thank you.

Best regards,

—
xx
Customer Support

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23.1.2025 'klo' 23.22 (10 päivää sitten)
-> info

Hello
Attached are the requested images and the 3MF file. On a textured plate it had no adhesion at all. On the second test I manually ramped the temp to 380 (from the tune menu), and it worked (perimeter failed as temp was not yet high enough). On smooth sheet (with Magigoo) the adhesion was better, but the typical PETG gloss was missing. The sheets were wiped with IPA and on the smooth PEI Magigoo was added.
PETG 280 vs 230C.jpgGeneric PETG (230C) on textured plate .jpgGeneric PETG (230C) on textured plate closeup.jpgPETG (280C) on textured plate.jpgGeneric PETG (230C) on smooth plate.jpgGeneric PETG (230C) on smooth plate closeup.jpg
The problems mostly happen with PETG. Have tried multiple different spools and dried them first etc. and always the same. I earlier printed dozens of perfect PETG prints.

Juha

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27.1.2025 'klo' 17.28 (6 päivää sitten)
Prusa support -> me

Greetings,

Thank you for your reply.
The hotend can only heat up to 290 degrees, not 380 degrees.
Please do not heat up the hotend more then the specified temperature for PETG in slicer.
The textured sheet needs to be cleaned more in order for the prints to stick.
Make sure to use at least 90 percent IPA. the textured sheet need to be first washed in hot water and soap and rinsed well before cleaning with IPA.
This is only done few times when sheet is new, afterwards only IPA is enough. Make sure to rinse the sheet very well after washing in soap and then try using only IPA.
Make sure not to use any Magigoo on textured sheet.
Thank you.

Best regards,

—
xx
Customer Support

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27.1.2025 'klo' 17.41 (6 päivää sitten)
-> info

Hello

Frankly I find the advice strange.
I do know how to print and how to maintain the sheets. I printed dozens of succesfull prints on PLA, ABS and PETG before the problems started. I even tried a brand new PEI sheet and same problem.

There can be multiple different issues which might or might not be related (like the z xslibration issue I had earlier), but the main problem seems to be the temperature. With the standard slicer temperstures the filament does not always even come through the extruder, but it gives continuous filament stuck problems. PLA and ABS sometimes works but PETG fails 100% of the time.

When I set the temperature 20-50 degrees higher than profile, it prints normally. PETG prints do not fail when I set the temp to max 290c (I had typo in earlier mail).

I'm pretty sure the temperature sensor is damaged. I can ofcourse try to replace it or the whole hotend myself, but I was really expecting better support from you.

Juha

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27.1.2025 'klo' 17.54 (6 päivää sitten)
-> info

These are some prints by me on this printer and now it does not even print the first layer test with the normal temp settings. The problem is not that I forgot how to print or my build plate got dirty. Something is broken on the printer.

Juha

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28.1.2025 'klo' 18.03 (5 päivää sitten)
Prusa support -> me

Greetings,

Thank you for your reply.
If the hotend was the issue the printer would show a temp error on screen. Prints adhere to the smooth sheet and not on the textured sheet, because textured sheet needs to be cleaned more to in order to adhere.
Make sure to use at least 90 percent IPA. the textured sheet need to be first washed in hot water and soap and rinsed well before cleaning with IPA.
If you still decide to replace parts regardless, only the temperature sensor is sufficient, not entre hotend.
Still the temperature sensor issue would display on the LCD if it was damaged.
Thank you.

Best regards,


—
xx
Customer Support

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28.1.2025 'klo' 18.19 (5 päivää sitten)
-> info

Please move this ticket to someone else.
You clearly have decided that I'm a stupid user who does not know how to clean the sheet and it seems impossible to change your mind.

I have provided clear evidence that it has nothing to do with sheets. Prints fail on smooth sheet and textured sheet the same way, although the first layer sticks better to the smooth one. I also tried a brand new, never before used sheet, and it is the same problem.
Getting filament stuck -error all the time in normal temps, before filament even hits the sheet is a clear indication that it is not a sheet issue.
Also with PETG layers do not adhere, and the glossy color is missing, unless I ramp up the temperature. I can print "normally" now, but I need to set the temperatures wrong.

Also if you know anything about printing you know that if the temperature really was 290 degrees on PETG you would not get perfect prints.
In forum I can see identical case where Prusa replaced the sensor. https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-how-do-i-print-this-printing-help/petg-matte-weak-layers/

Juha

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29.1.2025 'klo' 14.26 (4 päivää sitten)
-> info

benchy.png
Dear Prusa Support Team,

I appreciate the time and effort you have put into assisting me with troubleshooting my Original Prusa MK4S. However, after extensive testing, I strongly believe the issue is not related to bed adhesion or build plate maintenance but rather a temperature sensor calibration problem.

To clarify some points regarding build plate preparation:

I always clean my sheets properly using hot water and dish soap, followed by a wipe with high-purity (99.9%) isopropyl alcohol. This is done according to Prusa’s own recommendations.
I am well aware that Magigoo should not be used on textured sheets, and I have never done so. I only use it on the smooth PEI sheet when necessary to reduce adhesion, not to improve it.
The issue persists on both a well-maintained textured sheet and a brand-new, never-before-used smooth PEI sheet, so it is clearly not a contamination issue.
The real issue appears to be temperature-related:

My printer frequently reports "Filament Stuck" errors before the filament even reaches the bed.
PETG prints exhibit weak layer adhesion and an unexpectedly matte finish when printed at the default 245°C, which suggests under-extrusion due to insufficient temperature.
When increasing the temperature to 290°C, the print quality significantly improves, despite the fact that PETG at an actual 290°C would normally cause excessive stringing. This strongly indicates that the reported nozzle temperature is inaccurate.
I have documented my findings in a video comparison and attached image, which clearly demonstrate the issue. Given the evidence, I kindly request this ticket be escalated to a senior support representative who can assess whether a faulty temperature sensor calibration could be the root cause.

I appreciate your support and look forward to a resolution.

Best regards,
Juha Lilja

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31.1.2025 'klo' 20.22 (2 päivää sitten)
Prusa support (person 2)-> me

Hello Juha,

Thank you very much for the detailed description and the pictures.

We would not nesseceraly recommend using soap and water, we usually only recommend this once a year.
Isopropyl alcohol ( at very least 90% ) and kitchen paper towels are just enough to ensure proper adhesion.

Furthermore, based on the pictures and as my colleague has previously mentioned, the adhesion is very likely the root cause of your issues.

Any temperature-related issues would be reported by the printer itself by giving you a thermal error, if you dont get any but still insist on this being an issue of either heather or thermistor, you can have them measured by multimeter to see their resistance which would either proof or deny that they are faulty, the guide for measuring can be found here - https://help.prusa3d.com/article/multimeter-usage_2117​

Many aspects can  play a role in this as moisture of the material, ambient temperature, if the correct sheet is used with the correct material, or overall conditions that are required to print specific material are met, you can also find all listed requirements for our materials on our website here - https://help.prusa3d.com/materials
If they are meet, and there does not appear to be any thermal anomaly going on with the printer, its safe to assume the adhesion is the issue.

S pozdravem / Best regards
—
yy

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31.1.2025 'klo' 20.41 (2 päivää sitten)
-> info

Hello

Thank you for your reply. How can I get your mind out of the bed adhesion. That is not the root cause. I'm 100% sure of that. The problems started all of a sudden and consistently happens on 3 different build sheets. The same issues happened also with a brand new sheet.

Also I'm quite experienced in printing. I only clean the sheet when needed. Maybe it is my bad english or strange setting of the questions, but feels like whatever I answer, just enforces the feeling that I'm an idiot who either washes sheet too often or too seldom.

Also, as I have stated earlier, on normal temperatures I get filament stuck error before the filament hits the sheet. How can that be a sheet problem?

The fact is thst I get perfect prints when I set the temperature very high. If it is not thermistor, it could be partually clogged nozzle or something, but it feels unlikely that in such case just raising the temperature would fix all.

I'll see, if I can measure the thermistor, but I'm just getting tired on this whole thing. In web forums 90% of suggestions are about sheet maintenance, but from official support I really would wish for more creative ideas to get my printer fixed.

Juha

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1.2.2025 'klo' 10.37 (1 päivä sitten)
-> info

Hello again

I'm still trying to get my hands on a multimeter. Meanwhile I did one more test print. I'm a simple guy, a master of engineering by education. Please feel free to gather everyone from the support team to see the images and the video and try to find a way to explain to me, so that I understand, how my issues are caused by adhesion problems?

For this test I created a special gcode file (attached), where the same test object is first printed with the generic PETG temperature (245) from Slicer. Then  on the same sheet it is printed again with 290 C. In both cases the first layer is printed with 285C. The reason behind this is to minimize the number of variables and to see if there are problems also in other areas than first layer adhesion. As you can see in the video, in both cases the first layer prints perfect and adhesion is good. On the 245C version, I needed to cancel the object in the middle. The 290C version is not perfect, but better.

The temperature (thermistor) of course might not be the root cause, but can simply mitigate the issue caused by a nozzle problem or something else. This is where I need your help, if you can first admit, that bed adhesion most likely is not the root cause here.

Juha

Video: https://youtu.be/XwkDeeS_cC

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1.2.2025 'klo' 10.45 (1 päivä sitten)
-> info

Youtube butchered the link. Here https://youtu.be/XwkDeeS_cCc
Juha

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1.2.2025 'klo' 14.45 (1 päivä sitten)
Prusa support (person 2)-> me

Hello Juha,

No problem. I am afraid that this issue has been already revised by two agents upon your request to talk to somebody else and we came to the same conclusion.
If you insist on this not being a root cause of the issue, we can only recommend you consider a factory repair at this point.

I am sorry to hear that you are getting that impression, you can rest assured its in our best interest to help you as best as we can.

As for stuck filament, there might be lot of aspects playing a role in this.
From way too tight idler screws, incorrect temperature settings, incorrect height, and so on.
We would need to revise the setup alongside the 3mf as well.

Such an issue can be rather easily checked by either performing a cold pull or swapping the nozzle for a new one. Furthermore it's important to consider that each filament has different temperature requirements. PETG from us can have a different temperature requirement than PETG from a third-party company.

Sadly as was already mentioned this issue should be rather easily fixed by proper maintenance.
If you believe that has been already done, we can recommend sending the printer back for a service check. You can find more information about factory repairs on our website here:
https://help.prusa3d.com/article/factory-repair_267131


S pozdravem / Best regards
—
yy

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1.2.2025 'klo' 14.45 (1 päivä sitten)
Prusa support (person 2)-> me

Hello Juha,

As already mentioned this issue has been discussed and switched between two agents. From both pictures and your description the incorrect maintenance and possibly even incorrect settings for said filament ( based on the previous message ) can easily lead to such issues.

I am afraid that sadly we cannot read any specific settings from gcodes, if you wish from us we revise your print files, we have to ask you to provide us 3mf file.

It can be issue as well if the thermistor gives you an incorrect temperature reading, which we can only confirm or deny by having it measured by a multimeter.
I am afraid we have no means to deny or confirm that without proper revision of the cleaning and maintenance which was previously recommended by my colleague.

S pozdravem / Best regards
—
yy

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1.2.2025 'klo' 14.46 (1 päivä sitten)
-> minä

Hello Juha,

Thank you for the YouTube link.

S pozdravem / Best regards
—
yy