Why was Māui having trouble with his transformation powers?

Question

After Māui and Moana escape from the Realm of Monsters, Māui has some trouble with his transformation powers - like, having a shark head.

And then, a little while later, he has no problem at all - he can transform perfectly well, without having actually had things change very much.

Why was Māui having trouble with his transformation powers?

Answer 1

I think it was due to being rusty using his hook. It was a long time since he last had possession of his hook. Also, we don't see the progression of him "getting used to it"