Yeah, I tried when I was in Goldenrod, and then again for the past few days while I've been in Mahogany Town, but he does the same thing every time. I put him in the healing machine at the PokéCenter this morning while he was still inside his pokéball, but it didn't change anything. I guess that I could have Fearow fly away with all my pokéballs so Yamask can't get back in, but with how he's been acting that seems kind of mean.