There really seems to be an issue with the camera focus. I've opened a dispute with "Blackview Official Store" on Aliexpress because of it, but the people responding there don't seem to take the matter seriously.
Your application seems to do some kind of unsharp masking (USM, https://en.wikipedia.org/wiki/Unsharp_masking
) to "enhance" the image, instead of fixing the focus issue.
This has the effect of adding a lot of noise to the picture (especially visible on low light conditions) and doesn't fix the focus issue. I'd be glad to help fix the issue, but without the code it's hard to do
Here's an example of a picture (it works worse with focus at infinity):
Here's an experiment made with a black-white pattern, which shows both that it's not in focus, and that the software uses USM on it: