I’ve had the same issue, in a short animation with my updated OC as I scaled up from feet to head, between upper legs to lower torso, a part of lemon’s arm was suddenly detached despite not being movable, a separate Stickfigure or anything like a polyfill, it just suddenly broke off and then reattached itself.

I didn’t record because I thought it was something random and unlucky but from what you’ve shown, it looks very similar to my experience only lessened.