Sure. In august I watched my senseis not pass a shodan going for his Nidan because someone (not a Sensei) told him he didn't have to learn kata kanku dai. I said to myself, Say Huh? Why he listened to somebody other than a sensei, I'll never know, because I didn't ask him. I myself didn't pass my first orange belt test a year ago because due to circumstances I wasn't on top of things that night. Shrug. Stuff happens. I did get it later, though, when we retested. So yeah, people fail.