I found three friends to play Starground together.
One of them tends to Alt+F4 to any minor inconvenience: it happened twice, and each time it also closed the game instantly for me and my other friends.
I hosted the session and have a really stable and powerful WiFi connection.
It does not really look like a crash, the game just closed, no error message.
Later, I was just with another friend, and it worked as intended: when he leaved, I could stay connected to my own session.
(by the way, I love this new update!)