@motomulder I had QA test this on Xiami and we didn't find that the exported (save to phone) video was of bad quality.
Don't hesitate to share more info as well as the final file so we can have a look. Thank you.
@motomulder Ok I understand now. You're sending me a GoPro Plus link and it's "normal" as the quality isn't the full one.
Please, open the link on a computer, once on your video page, tap on the ... bottom right corner and select: download original quality file.
You can check the result on your computer, it will look better.