There's a bug where rigidbodies can 'implode' after which they will be invisible, but able to be grabbed from anywhere by vr users, ruining the world instance. (vr users will have a constant 'Hold to grab' message and be unable to grab other world items)
This is particularly bad for puzzle worlds as it will stop your progress.
Maybe related to this bug, I noticed that my world's player count was not decreasing for instances where this bug occurred. I joined one that said 17 people, and there was 1 person there, and the bug. I joined another with 7, same thing.
Edit: This may have been because i was accessing the world's menu by clicking on myself in the social menu, and it didn't refresh?
To recreate the bug, have a world with a lot of rigidbodies, and try bashing them around a lot. (It might only happen to pickups?)
If an item with a chair on it has this bug, and you manage to sit on it, (which happens quite easily because instead of 'Hold to Grab' you get 'sit' everywhere) it will crash the game.
If a bugged item is teleported with a trigger, it can fix the problem for that item, so I guess it's something to do with the transform breaking.
This bug has existed since the old Unity version, but has definitely become more common in the Unity 2017 version.