Genuinely curious! Did anyone find out that a part of their original hypothesis was wrong? Did another group disprove your work before you finished? Or, as the title said, did you reach a point (late PhD or postdoc stage) where you discovered that your original project idea was overwhelmingly wrong? To the point that you did great research towards an idea that was essentially garbage? Even if a garbage idea doesn't necessarily result in a failed PhD, I would love to know how people navigated this situation...

I've not personally heard of anyone disproving their own Ph.D. thesis. However, John Forbes Nash Jr -- the creator of the Nash equilibrium -- later recounted how he later believed his theory, whilst applicable to a variety of areas, such as nuclear strategy, actually performed very poorly when applied to social behaviour and humans in general. He put this down to his theory's over-reliance on the assumptions that humans predominantly act rationally.

Wizard

I don't know if anyone has fully disproven their thesis but my supervisor's thesis evaluated the technical side of a novel bioenergy process. Then after she passed her viva wrote a paper saying the economics don't work and it never will make any money. So does that count as disproving your work?