Sometimes, hearing a writer or director openly discuss one of their own films can be really illuminating; they can unearth hidden meanings, behind-the-scenes stories and respond to criticism in a constructive manner. Some, for better or for worse, even elect to revisit one of their earlier works in a new film, and flesh out a mythology they personally felt needed to be explored.
For the most part, this is all fine and dandy. Issues only really start to arise when they explain things that didn't really need to be explained in the first place, whether that be a plot point left open to audience interpretation, or a criticism they think they can refute. Some filmmakers get so invested in their own film's critical post-mortem that they can end up dragging the feature down altogether, as has become increasingly apparent over the last year in particular.
Press junkets, evidently, are way more precarious than was once thought.
Some filmmakers just don't seem able to let their work be, and it can often have the adverse effect of either demystifying a beloved story, or - in extreme examples - toxifying a project altogether...