Animation is wrong when the player does it but works on rig?

I am currently trying to make an animation that makes the player hold a ball. When I animated it on the rig, it was fine. Playing it on the rig I animated it on is fine as well, but when I try it on the player, it looks like this:

Photo

This is for every animation I try to make. Ball position is good! It's the arms that are not in the right place. I think this is for other parts of the rig as well.

Rig: Boy Rig R15