Here’s a fix. Though you need to NOT be on PC. You can fix your duels on your phone and then go back to pc afterwards but the fix only works on phones (I use an android)
So you start your game and go to the duels screen. BEFORE pressing Resume get your finger ready to press where the chests would have been. Though they do not appear visually you can press on them and hear them open. once it’s done your previous run will be finished and you will be able to start a new one on PC. You got to do it fast.
It’s the best I’ve got but hey, it works.
EDIT : blizzard talks about it here. Stuck on Duels Rewards Screen
even with the fix this is so annoying I almost don’t play duel anymore.