The animation was intentionally jarring with it's lower framerate for a specific reason...
it was showing miles as he's unexperienced as spiderman. At the end of the film his framerate of animation matches everyone elses at the 24~ fps, while during most of the film he was at 12fps. It was also to give it a more "comic book" feel
Personally while I respect the artists direction for this, it was so jarring and kind of pain inducing on the eyes, that If there's a sequel I really hope they animate things more fluidly.
