As you can see in this picture the arms on the original animations are perfect, yet when played on a player they are out of place.
The arms have been rotated 90 degrees to allow the elbow joints to bend downwards if that matters.
I’m not sure if it has something to do with scaling or?
That happens to me as well, on some of my animations, and it seems the more I try to correct it, the more out of place things get. Not sure why it happens, but like you said, it will be fine in editor with maybe a very slight out of place happening, but when played, it really messes up. Usually I have to just start out with a new animation, and try to limit the amount I rotate and move the parts. Seems the less you rotate, the better.
I had this issue before too, I changed the Avatar Scaling to Standard and Avatar Animation to Standard and it fixed the issue.
