Mozilla Nightly/ Firefox crashing feedback

For MANY months now- probably at least the entirety of 2019 so far (four and a half months) my Nightly has been freezing after being open for a while. It produces the error window:


"Warning: Unresponsive script

A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

Script: chrome://global/content/elements/browser-custom-element.js:448

[checkbox] Don't ask me again

[Continue] [Debug script] [Stop script]"


The script it shows changes every time. The other screenshots I took of it say:

"Script: chrome://global/content/customElements.js:223"

Script: chrome://global/content/bindings/scrollbox.xml:291"


On May 4 (10 days ago) Nightly actually FAILED TO LOAD ENTIRELY! It just produced a blank window saying:

"XML Parsing Error:
Location: chrome://browser/content/browser.xul
Line Number 31, Column 1:

%browserDTD;
^"

When this happened I just used Firefox for the next day until I assumed Nightly updated, at which point I installed that update manually, but the habitual freezing-after-staying-open-for-a-while still happened every time.

I assume the only reason this happens is because I disabled every button on the menu bar except "Help" via the use of the following script:

"#file-menu,#edit-menu,#view-menu,#history-menu,#bookmarksMenu,#tools-menu {
	display: none !important;
}

#helpMenu"

To use the script I followed these instructions (I'm paraphrasing them):
1. Enter "about:support" (without quotes) in the URL bar
2. Ctrl + F "Open Folder" then click it
3. Create new folder called "chrome" (lowercase, no quotes)

And after that the guy gave me a file to put in there named "userChrome.css". But he only included a way to get rid of the "bookmarks" button from the menu bar (since that was my question, since it was freezing my browser for minutes every time I accidentally hovered over it.) So someone else taught me how to disable the other buttons if I wanted:

I'll just quote the second guy's instructions verbatim since I'm too lazy to paraphrase:

1. f12
2. settings
3. tick last two boxes on the bottom right
4. dev tools/ ctrl-alt-shift-i
5. inspect/ styles
6. inspector/ click the arrow to select what you want to hide
7. style/ select userChrome.css
8. put that id there
9. click save changes

I was really not even sure how to find these instructions and all that, so I was just hoping it would just stop eventually. But it never did, for months. It was horrible. I was hoping by my bothering to submit everything I know that you guys could fix it.

Also, random other thing, like 2/3 years ago now Firefox used to have tab "favicons" when you opened an offline image in a tab (for example, "file:///C:/Users/user/Desktop/apple.png" in the URL bar). I really hated how these tab favicons behaved. There was no stansard for loading them at a 100% rate; instead it failed to load if an image was larger than like 1200x1200 pixels in res, but it would load sometimes if you didn't return to the tab for a while, then refreshed, as if to catch it off-guard when the browser didn't decide it won't try loading its tab favicon. It was truly horrible. But one day you guys just removed the feature altogether instead of fixing it to load tab favicons at a 100% rate. I complained about it so many times across the years... then I just eventually stopped... but I still mention it whenever I complain in this way anyway... I know I'm the only person in the world who could ever care about this in the history of time... I didn't even realize at first the proper terminology was "favicon"... but won't you at least add back the feature when it pretty much sucked, rather than just remove it for years and years only hurting me...