I was going to post this as well. This is critically game breaking for BO3. My experience is that rather randomly (some games I can use my sideboard but other games I can’t), but almost every match my sideboard becomes completely unresponsive to adding cards to my deck. I can remove cards from my deck and put them in my sideboard but I cannot add cards back. If I remove a card before attempting to add a card, I cannot even submit a legal deck unless I restart to client and just re-submit my original 60 main deck (in other words if I move a card from main to sideboard and then can’t put one of my sideboard cards in my main to replace it I get the “illegal deck size” error).

This bug appeared at the same time I became entirely unable to view graveyards if I don’t have priority and feels similar in that both my sideboard pool and graveyards just go completely unresponsive.

I finished rank 28 constructed last month and am pre-qualified for Qualifier Weekend and if this bug persists to then I will be greatly disadvantaged and seeking compensation.

I am using Android OS iPhone 13.

EDIT: I no longer believe the ability to use sideboard is random as initially reported. It seems that if you win the game you can use sideboard normally but when you lose a game you are blocked from adding to your deck. This seems, again, to be some how related to the graveyard bug of priority some how applying to the sideboard zone. This is making best of 3 essentially unplayable and again, I have qualifier weekend this weekend and am essentially stuck without use of sideboard. Fix this.