Left on 'Roster' screen despite game starting in duo queue

[justsomeclouds]

Was searching for a match with a friend. He confirmed his roster and entered a match, but on my client it said he hadn't confirmed a roster and I didn't enter the match. We waited for a while but it did not change or update in any way. Restarting the client showed the 'rejoin match' button but it disappeared as soon as I pressed it (though that might be because the match had been cancelled / abandoned by that point).

I saw a related bug about spectating - I had not interacted with the spectate function at all, just to eliminate that variable.