Possible Hand IK or Animation issue?

Hello, so i originally built my projects player controller on the UE5 skeleton which had all animations and everything working fine. It wasnt until a few hours in where i needed to switch it to the UE4 skeleton so it would work with my clothing meshes. So i swapped basically all that needed to be done within the Animation Blueprint (such as spine bones as my player has a leaning mechanic).

Great, player works fine moving around and the clothing meshes match perfectly, though i noticed one thing wrong and its the arms/gun ik bones.

Images for reference:

Doesnt matter what animations i choose, the hands get messed up. Right hand wont attach the gun properly (rotation is off, and no matter what i rotate it to it wont change) and left hand just sticks out.

Not sure what to do here, any help is appreciated!