I'm glad the problem is solved.

I ran more tests, and it's definitely not your mod — sorry fot the false report. The issue came from the pawn editor and its save profile, which bugged when I was managing all my mods.

It's ok, I don't want my class to have bugs.
I wrote in the Custom_Class_Defs file:
<isMage>true</isMage>
<isFighter>true</isFighter>
The class is based on the template from the RoM developer https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2114216280 and the classes of the Kure's Rimworld of Magic Class Expansion Pack mod, so it's strange that the bug only occurs with this class.
I myself played with my mod for 3 days on a medieval build, which consisted of about 130 mods, and did not find any bugs related to the class.

@dracks Hello, it looks like there is a bug in the A RimWorld of Magic mod itself, people in the comments have encountered the same problem. Try putting the A RimWorld of Magic mod as high as possible in the mod loading queue, maybe it will help.

This is my first attempt at "modding", so if there are any mistakes, please write about them.