Everyone screws up. Everyone. All the time, in fact, seeing as how life is just a long stream of tripping up with the occasional instance of someone managing to land on their feet and make it look intentional. So it stands to reason that even the most talented among us have projects that make their ears turn red with embarrassment.
Likewise, a filmmaker has at least one film under their belt that they would rather fake their own death than acknowledge having made the thing. Regardless of the quality of the director in question, this is one experience that is universal. But embarrassment, like all emotions, is a spectrum, and some filmmakers are more ashamed than others.
Whether it's because outside events caused their film to fall apart during production, or because directors are fallible human beings like the rest of us and just flat out made a bad product, these filmmakers have at least one movie under their belt that they would really just rather not mention in polite company. And, truthfully, it's probably for the best that way.