I have absolutely no clue on steps to reproduce, but sometimes, when you load into an area, chat will stop working, and you will be unable to enter terminals/leave terminals/teleport.  Logging out from this state will greet you with a black screen.

While in this state, you still have a normal ping, can run around the world, complete missions, see other people running around, etc, so you still have some connection to the server, just can't do many meaningful interactions.