If two players join as the same side/country/empire during the same turn (lets say egypt empire is open, and two guys join and both select it), second person to select it automatically loses instantly.
Looks like it doesnt do the "sorry this is already chosen" at the selection stage. I wonder if the problem is when there is more than 1 country in an empire (if Egypt is egypt + tunisia + libya) and one joins as egypt choosing 1 country and another as egypt choosing another country?