Yikes, that's not good! The cause was path constraints from older projects did not have their Y mix set to the old translate mix. It defaults to 1, which moved bones unexpectedly.

We've fixed it in 4.0.62-beta, which we'll release today. If you need a fix sooner, it could be fixed manually by setting the Y mix for each path constraint in the setup pose (keys in animations don't need fix up).