Hello, I'm still fighting with breaking meshes.
I noticed something curious that's definetly not due to some mistake of mine.
I have file #1 in which a certain mesh appears wrong on a specific animation. I take a backup copy of said file in which the mesh in that specific animation looks correct, import skeleton and drag the mesh into skeleton #1 and replace the breaking one. I opened file #1 and #2 side by side, these meshes look exactly the same in setup. Same vertices, same weights, same everything.
In file #1 though, if I go back to the animation, the mesh is deformed differently than file #2
It's the exact same mesh in the exact same pose. I even imported the animation from file #2. Compare them side by side: correct in #2, twisted in #1
???

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Hello Fainder, are you absolutely sure the exact same bones are present in both skeletons and positioned in the same way?
That you didn't change the influence of a constraint or the constraints order?

What you're describing is an extremely bizzarre behaviour, if you can, please send both files to contact@esotericsoftware.com mentioning this post and the mesh to look at.

There are no constrains on the bones that influence this mesh. I might have added a bone since the backup version, I'm not sure, but even if I did, it doesn't influence this mesh or the bones it's linked to. Probably not though, since I imported the animation from the backup correctly
This happened a few times though, I just now noticed that in fact the meshes are identical in setup mode. So in this specific case it's a simple arm mesh linked to a few arm bones. In other cases it could apply to more complex meshes. This is a simple case
File sent anyway, thanks!