For the purposes of this test, I set the backup interval to its lowest value: 0.05, or ~3 mins. All tests were conducted in the same singleplayer world except for in different modpack versions. This is the approximate order I ran the tests in.

- Test Singleplayer w/ just EnthusiastiCraft 1.4.1.
-- Test one: Backup worked.

- Test WorldPrimer (Note: I don't remember what version of WP or modpack I used here :/).
-- Test one: Waited 10+ minutes, no backups.

- Test 1.4.1 w/ WorldEdit & WorldEditCUI.
-- Test one: Backup worked.

- Test 1.4.1 w/ Schematica + Lunatrius Core.
-- Test one: Backup worked.

- Test 1.4.1 w/ WorldPrimer 0.6.0-dev.20190525.121747.
-- Test one: Backup worked.

- Test 1.4.1 w/ WorldPrimer 0.6.0-dev.20190309.202458.
-- Test one: Backup worked.

- Test 1.4.1 w/ Misc server-side-only mods: DiscordIntegration, Dynmap & Dynmap Blockscan, and Storage Drawers Extras (SDE removed from 1.4.1).
-- Test one: Backup worked.

- Test Singleplayer w/ just EnthusiastiCraft 1.4.0.
-- Test one: Backup worked.

- Test 1.4.0 w/ WorldPrimer ...458. This is the one I expect to break.
-- Test one: Backup worked. Hmmm.

- Test 1.4.0 w/ WorldPrimer ...747.
-- Test one: Backup worked.

- Test 1.4.0 w/ DiscordIntegration, Dynmap & Dynmap Blockscan.
--

- Test 1.4.0 w/ DiscordIntegration, Dynmap & Dynmap Blockscan, and WorldPrimer ...458.
-- Test one: Backup worked.

- Test 1.4.0 w/ DiscordIntegration, Dynmap & Dynmap Blockscan, and WorldPrimer ...747.
-- Test one: Backup worked.