Hi,
The skeletons are different but “technically” the same. It’s the SK_Mannequin_Arms and I got several of them from different asset packs I downloaded. All the bones and whatnot are the same.
I also had a similar issue a few days ago with my rifle arms which also was incorrectly pointed and twisted. Deleting the animations and retargeting them again solved it, I tried the same with my new problem arms, but it didn’t solve it. Also, in both instances I had closed the project and everything was working correctly and it was only when opening the project later on that immediately the arms would have this issue.
Another thing as well is that the arms cannot play animations at all, even just in the idle animation, the arms are all twisted and pointed incorrectly. I rechecked all my sockets and everythings correct there.
Could it be a bug with UE5 and when starting the editor it might cause an issue with the IK?