iCloud Inconsistent Frame Rate at Full Res Download “KEEP ORIGINALS”

As I am currently 48+ hours into my 256GB iPhone 8 Plus back up with my paid 2TB icloud storage I went online to review the quality of my videos on my iPad and downloaded a handful of files to test out the “Keep Originals” option in full res. It appears the video quality is great and in 4K but the frame rate seems to be bouncing from 20-60 FPS rarely staying at 60 FPS for more than a couple seconds at a time... Being a multimedia specialist this is very frustrating as I expected the file to be transferred fully in 60 FPS keeping its original format, frame rate and quality. Is anyone else having this problem? I haven’t the time to fix the frame rate on 1000s of videos.