Now something new (to me) :
Still Firefox 50.0, just ended a game (lost it, game still active but I'm back to the lobby).
I get an error popup when coming back to main lobby : "The method ListRooms can only be called when connected to a game". The OK button does not help : the popup goes away, but no game listed (and no player listed as connected, it says "Connecting" instead in the left pane, with the 6 hexagons animated logo).
Everytime I click the "Refresh" button on the right side I get the same error...
A reload of the whole page fixed it.
Hope this helps improving.
Also got disconnected once in a previous game, but I think this has been mentioned before.