So I'm trying to improve my "hats off" animation and to do this I've duplicated the hat model and placed the copy in my character's right hand.

Here's the animation, the animation starts with the hat on the head, my character's arm moves up to the hat, holds it there for a second, the models seamlessly swap, he takes off his hat and holds it to the side doing a little bow, he puts the hat back, holds it there for a second, the models swap back, and he moves his arm back to its normal position.

That's how the animation both works on paper and in the editor.

Here's where the problem comes in, when using this trick in game the first half of the animation runs fine, the second model swap however fails and the hat suddenly jumps to his head before the arm gets in position, then he moves his arm down with the handheld hat model.

Now it is possible to make this animation without this trick, but small quirks in the animations make it look really odd since the part is 100% tied to one parent or another. Basically, it means fighting the movements of the limb to try and control both it and the object at once.

This bug is back. (Technically on some versions it never left.)

Basically all you need to know is toggling the visibility of a part on or off in an animation causes it to become stuck in the changed state, briefly glitching out when it should have switched back.

This bug appears to have been fixed in the latest version.