I was battling when suddenly it started lagging a bit and I was like ‘ok’ but then it started just doing the least attacks for everything even when I chose a different attack, and when they died, it just picked a random one instantly and put it in. This happened 4 times in a row, and I lost many trophies from those glitches battles, and slipped out of arena 5. The first two times, I was playing on data, and the next two I was on a stable wifi connection. Maybe if the game detects that something is preventing it from functioning normally, it can exit the battle without losing or winning any trophies.
This phenomenon has occurred to me before, various times.