I feel like we both agree that a time gap producing a massively unexpected shift in narrative is dumb. It can easily be put down to laziness or bad writing.

However - I don't see the problem with it. What if the logical path a story should follow is inadequate to produce a sequel?

The best example I can think of is The X Files. Scully sees aliens in almost every fucking episode. And then at the start of the next episode she goes back to not believing in them.

If she saw one in episode 1 of the show (which she does) and then simply agrees with Mulder that aliens exist every time Mulder suggests it's them - suddenly the show has no dramatic conflict. Now Mulder isn't trying to solve cases AND prove Scully wrong if she just agrees with him.

It's complicated. As with everything, you can do it well or you can do it badly. But there's no rules to film.