Film rate content on any interlaced channel deinterlaces to 29.97 fps rather than 23.976 fps, resulting in jerky motion. Commercials do not appear to have this problem. Does this have something to do with the way certain content is tagged? A less-than-ideal solution would be an option to simply perform some sort of bob deinterlacing universally. This would introduce more duplicated frames, but would minimize jerkiness.
EDIT: This is on a Fire TV Stick 4K.