If you leave a multiplayer game back into a lobby with no respawn and you're out of bots slot to slot in then rejoin the game. You will be stuck spectating only one player in first person mode and you cannot switch to anyone else. While you are stuck in spectator mode, you cannot use the arrow keys to switch to another person nor spacebar to switch camera view. You can, however, control the command menu of the player you are spectating. I have not fully confirmed whether action menu worked too, but I managed to get into a player's inventory before a game ended during the test.