So here is 2 problems that have been present for months but i never reported.
If you are in a Plaza and a friend sends you an invite to a gameworld, accepting it does nothing. The only way to accept it is to leave the Plaza and accept from the main menu.
The second problem is joining a friends gameworld that was made through the Plaza. If you accept an invite or try to join through the steam overlay it only sends you to the Plaza they were in and not the gameworld they are currently in.
The only way to join a game that was made in the Plaza is to try and find them on the server list from the main menu.