Lulu polymorph

When I was playing Lulu I would polymorph an enemy katarina and it wouldn't take any effect even though the ability would go on cooldown. Sometimes it would polymorph her but whenever she had her ultimate going anytime she got a reset she could use all of her abilities. I believe that it may only be while she is using her R ability but I can't say for sure as it was hard to tell if this was the case. I have seen this bug in several games against katarina and on several occasions in each game.