Repro steps:
Use SteamVR while using the Oculus Rift.
Wait to load in.
Press the B button to open your menu.
Menu opens.
Menu does not open. If you go around and try to interact with things in the world, things don't work either. It takes a few seconds to teleport through the door trigger, for example.
Once you've successfully used the teleporter, all the sudden the menu works...
This does not occur in the VRChat Home, so it may be related to some component in that user's world. They state that other users have experienced it in their custom home worlds.
This issue also occurs on Desktop.