It happened to me twice, before I started looking to report a bug foorum.
I had the same blank cards problem.
First time I faced aether deck with only 6 cards left in a deck, I won by decking him out (won aether pillar and graboid).
Second time opponent had -7 cards in a deck and I won and spinns were all emty, but I got extra
for each card winning spin, although no cards were won.
It needs to be fixed soon, can anybody connect Zanz or somebody who can fix this?