Have you ever seen a movie where it seemed apparent that the director unwittingly spliced together two different films

I know this will be misinterpreted by many, but I always feel this way with most of Stanley Kubrick's films (all of which I like A LOT btw).

Wonder Woman feels like that.
Also, Z For Zachariah, which starts out as one movie, but changes as soon as more characters are introduced - but not in a way that feels natural. And The Power Rangers; the Rita scenes feel like they belong to another movie.