Bizarre animation behavior on skinned meshes

I’m unsure if this is the correct category, but this has been a massive problem in developing our horror game with skinned meshes. Animations seem to do bizarre things when running them in-game vs. the animation editor. On some rigs it works perfectly fine, but on others, some animations just completely break. A large portion of development time was perfecting these animations, so it would be wasteful of our time and resources if we had to redo these animations.

Things we have tried so far consist of:

I know that seems like a short list, but I can’t think of any other solutions.

Videos of our team running the animations:

Strange behavior on rig when running the game

Animation behaving properly on other rig

Correct animation behavior through animation editor

Thank you for your help!