Minecraft 1.12.2

Obfuscate is a Library, which allows easier codding with player body parts or simply put "animating".
The RFP2 mod or Real First Person has preset settings of how the models / slots should look like and such. While that is completely fine, if you add mods/library that override those settings, will most certainly brake it, as this mod does.

MrCrayfish's vehicles mod is dependable with this library and uses it for many body parts positioning,
one of which is the head while inside vehicles that most likely overrides that setting.

Example when using MrCrayfish vehicle mod with RFP2 :

Is there a reason you have put this as an issue? If you haven't noticed a bug, please close the issue so that people can find issues more easily. If it's another mod, ask the owner of that mod to change the code instead.