As the title states. Myself and my friend group have been testing this and we can re-create it as an issue every time, even with lax firewall and router settings (DMZ being the most lax).
Two or more people from the same continent/country creating a game session via the gameworld ports can easily join and play, and then return to the lobby afterwards, but when two or more people from different countries try, the people within the same country as the host can connect fine, whereas the people from outside of the host’s country just hang there and eventually get returned to the main menu.
Another bug that spawns from this issue is that if somebody gets impatient waiting for the connection to the host/waiting for the connection to time out, and hits return to lobby, they are then unable to connect to any server until the client has been restarted.