Steps to reproduce:
  1. Players A and B join the instance
  2. Player A changes into an avatar with a chair/station on it, then back out of it. During this, player B sees them normally.
  3. Player B rejoins the instance and observes player A stuck on spawn (sometimes under/near/nowhere; maybe origin, world used for testing had them in about the same spot), spinning wildly, regardless of actual position or view direction of player A.
4a. If player A changes avatar into any other avatar without chairs, they will stay stuck.
4b. If player A changes avatar into any avatar with chairs, they will get unstuck for player B (late joiners will still see them stuck if they later switch to a chair-free avatar)
4c. If player A rejoins the instance (while in a chair-free avatar), others (including late joiners) will see them fine.
4d. If player A sits in a chair while stuck, they will be visible and audible from that chair. Once they get out, they're back to being stuck (tested with SDK2 avatar chair)
Tested with an SDK2 avatar as breakage-inducking (didn't test with SDK3 avatar), both SDK2 and SDK3 avatars breakage-fixing.
Screenshot of someone stuck (yoinked from https://feedback.vrchat.com/bug-reports/p/1095-rotates-sometimes-people-by-90-degree-to-the-left, looks close enough):