This happens even if the config file wasn't altered, and if it was altered, the values are kept in the current .toml file, so it technically is working... it's just the config folder ends up filling with new 'allurement-common-#.toml.bak' files every single time you boot up the game, adding a new one even if you left the old one(s) there.

Just tested this with only abnormals_core-1.16.5-3.1.1, allurement-1.16.5-1.1.1, and Forge 36.1.4 installed on 1.16.5. I ended up with both allurement-common.toml and a allurement-common-1.toml.bak file on the first run of the game.

It appears to be an issue with floating-point imprecision during parsing

Configuration file E:\Minecraft\CurseForge\Instances\...\config\allurement-common.toml is not correct. Correcting
Incorrect key enchantments.alleviating.Healing factor was corrected from 0.25 to its default, 0.25. 
Incorrect key enchantments.vengeance.Damage factor was corrected from 0.025 to its default, 0.025. 
Incorrect key tweaks.soul_speed.Damage factor was corrected from 1.5 to its default, 1.5. 
Configuration file E:\Minecraft\CurseForge\Instances\...\config\allurement-common.toml is not correct. Correcting