Packs Contained One Card Each, Missing the Rest
I just cashed in 3000 coins for 3 regular Dominaria United packs and went to go open them. The first pack opened normally, displaying all the cards on the screen. I still had two packs left to open, but when I clicked on the next pack it just showed me two rare cards at the same time, already revealed, and no other cards in the pack, and apparently that action consumed BOTH of my packs. I'm not seeing any other cards in my collection that could have been the undisplayed cards from those incomplete packs.
The UI displays only the rares when you open all packs at the same time.