Having triggered once, and tested a second time, it appears this is a repeatable bug (as of last Sunday):
Blitz a target holding the ball. Attacker has Strip Ball. Defender does not have Sure Hands.
Get Push on dice, choose to push target into a Stand Firm ally (other two push positions are filled).
Decline to use Stand Firm (allowing ball-carrier to be pushed back).
This should make the ball-carrier move back, dropping the ball and subsequently pushing the Stand Firm player back as well.
Instead, the game hangs, displaying connection error (though both players are still online, in-game). After about 30 seconds, the match aborts, kicking both players back to the game lobby.
I suspect this is connected to the old Strip Ball bug (didn't Strip if pushed into Stand Firm) made uglier by the new (for BB2) optional nature of Stand Firm.
(There is no crash report, because the game just ends the match prematurely, rather than crashing entirely)