Upload ruins video quality

I have this same effect with my Iphone 8. and its not in 4k. its 1080p at 30fps. I think it might have sometime to do with the shit cable I use but I do not have any other ones to try it out on. Any time I drag and drop the video files from my Iphone to my computer they come out all glitchy with artifacts obscuring the feed. The only work aorund I have found is this: Download the program called "IBV" iBackupviewer, it lets you explore your iphone backup that iTunes makes on the computer. iTunes backs the video files up without glitches or artifacts and in a different format vs when your drag and drop from the phone itself, maybe it uses check sums and corrects errors IDK? Once the backup is complete, close iTunes and launch IBV, navigate to photos and highlight the ones you want, max 9 at a time for free version, then extract them all, extract multiple times if need for over 9 photos/videos to a folder on your desktop and then try and upload the file from there. Please Note, if you extract photos from IBV will be in a different format called .HEIC and videos in .MOV, you can covert HEIC to JPEG/JPG/GIF easily and lower the size of the file substantially, and you can also convent MOV to mp4 and do the same thing. I use Gimp Photo editor and Openshot video editor to add in effects like watermarks or convert the files into lower quality so it does not take forever to upload to grow diaries. Good Luck, hopefully this fix works for you as it did for me. Hit me up in the DM and we can trouble shoot this a bit more if your still having issues.