I‘m not sure if this really was the trigger but:
It was past midnight and I (host) went to sleep in the co-op players bed because I was at that house currently.
The other player was not sleeping so normally the pop-up-text „Waiting for players 1/2“ should come.
Instead it ended the day and I could see how much money I made that day etc.
The other player did not receive this „end of the day“-summary-menu but got kicked out of the session.
The new day started and the player was not able to join until I ended the session and loaded it again.



