struggle move bug

[Soulassassin]

hello, my magnezone was fighting in the cave on victory road 3f kanto region. after an attack from one of the spawned wild pokemon all of my magnezone's moves were wiped and only struggle remains. I thought this was strange since I've never seen a move that does this action. after the battle I continued to fight for like an hour. all of these battles the moves remained the same. the pokemon still shows all the moves it's supposed to have but once in battle the pokemon only has struggle.