IMO it’s more to do with the instructors. I failed cat C twice after “training” with the worst possible school with the crappest trainers and I even successfully claimed some of my money back. I’d love to name and shame them but apparently it’s frowned upon in here but I don’t know why as it would be helpful information. I did my CE with a proper, professional school and passed first time with no problems. I know it can be difficult when you’ve already paid but if I were you I’d try a different school.
Good luck 