I see similar issues posted, on android app can sideboard fine between game 1 and 2. Sideboarding between game 2 and 3 I removed a card from my deck and was unable.to put any from my sideboard back in. Could not submit a deck and was stuck on sideboarding screen. Restarted and was stuck on waiting screen for 15+ minutes. Restarted again and was finally back to home screen.