thank you for the reports, I'll investigate since what you described definitely should not be happening lol
what release of the game were you playing on when this happened? (windows, androis, linux or browser)
Some more bugs, in Battle Frontier:
3. Thunder shock's adjacency damage doesn't break Illusion.
4. Battle Frontier music sometimes doesn't loop correctly?
5. The opposing pokemon sometimes show the wrong level. Hovering over it shows a different level on the card, presumably the correct one.
6. Sometimes when initially choosing the pokemon move to use during a battle, both move options show up darkened.
7. I somehow caused the pokemon and move selection/auto-battle/pre-battle/start battle/shop/items/quit game menu to become out-of-sync, where the fading in-and-out rectangle became one unit to the right of the actual selected option. It's probably related to the item selection screen, since when I went back to the item selection screen and back out, the display fixed itself.