So I watched this on Twitch. It worked, and it has worked for others since, so I wanted to share.
If they forfeit and you get the error message, just hit cancel, and don't do anything else. The timer is still running on you even though you can't see it. You will time out and get a warning with 1 timeout remaining. Then it will load and you can shoot like normal.
I don't play the showdowns, but figured I would share anyway. Hope this helps. Good luck!