Yeah i saw that line in the footage too, and sure for a true video bubble that wont do, but i assume this is a software fix.
4K footage allso appeared a little "soft" to me ? footage dident appear that crisp as i would expect.
Seemed a bit large at least compared to a regular actioncamera, but i do like tha as is 30 M waterproof, though that in itself include some perils to have the camera out there in the elements.
I would have preferred a single 4K camera and if it was able to do 1080 / 120 FPS i would be happy.