The Stargate SG-1 writers regretted the "3 shots from a zat-gun disintegrates" thing, and had zat guns only ever hit stuff twice for the rest of the show after they realized the mistake they'd made.

The problem was introduced to solve a plot issue in one episode - they needed a way for the team to get rid of the bodies they were leaving behind on a spaceship in one episode.

But plenty of other franchises just ignore things in the past as though they never happened, even up to and including characters.