Hi,
I observed multiple times that a player that has already been eliminated is chosen to start the round. When that happens, the activity "Place armies" no longer happens (thus no exchanging of cards), "Attack", "Regrouping armies", and getting a card (as long as your deck is not full yet) still happen. With any armies still on the board, the remaining players can keep looping through.
The situation is hard to reproduce, I have not pinpointed exactly how it happens...