Player avatars will stand where they loaded in even if the remote player has moved to a different location. It doesn't matter if players join all at once or join spaced out. Sometimes it only happens to some players, but most of the time it happens to everyone.
It is also possible to move items around even when your avatar isn't synced for other clients, but sometimes that fails too.
Checking the logs indicates that several nullref exceptions are being thrown which are likely related.
The bug can be most consistently reproduced in the following world:
vrchat://launch?id=wrld_b39acf40-9c60-4a75-824f-70c98fc2fede:3180~private~nonce(OozB1YIGh4ZFa2QidJLPfr8MnUe03t)