I read that if a Priest fails at an exorcism, he is never allowed to do another exorcism again.
Well apparently not in this case. But I have no idea how they regulate that. But they haven’t been very good about regulating their priests to begin with.
I don't believe that's true. From what I've read, the rite must often be performed many times.
Catholic Answers radio interview with an exorcist:
"Authorized exorcist Father Gary Thomas (the real life priest of the movie The Rite) reveals what it’s like to do battle with the enemy of our soul."