Netflix picture quality sometimes bad?

On Netflix I have the problem that some films are perfect to watch, but some simply have a really pixelated resolution. I've already tried changing the playback settings to high, but that doesn't help. Since some films work well, it can't be because of the network, at least I think. But even with the best will in the world, I can't imagine that the resolution for the problematic films is only offered so poorly, because there are sometimes things like "London has fallen", films that live from good graphics… Anyone knows what I can still do? I use the platform via the Amazon Fire TV Stick

Have you ever let the films run longer to see if it gets better? I can only explain it with a fluctuating internet speed.

I let it run for about 5 minutes and nothing happened… But I've already set the image quality to high, regardless of the network speed, the setting would also be automatic. Can it still be because of that?

Try with automatic. Are all films in school of higher quality right now?