I think I have exactly the same bug, but for my map it’s during the game session, it can appear between 5 and 20 minutes after the game has started (I don’t have a pre-game lobby).
The problem is very similar, playersare hanging, and then it crashes and sends everyone to the lobby.
https://forums.unrealengine.com/t/freezes-and-crashes-during-game-session/2350496