Priests are humans too, subject to the same weaknesses and temptations that everyone else is. Remember only Jesus was/is perfect. Breaking a vow of celebracy or any other mortal sin would be serious, but I doubt grounds for dismissal from the priesthood.
I’m sure there are some rules that may call for dismissal, I would think after all the fanfare, pedophilia would be one of them.
There may be many saintly priests, but I’m sure there are many who struggle like the rest of us.