From your previous posts: The problem has to be after the stream has been received and decoded, this leaves the firmware/driver that handles the DVI-out, the cable or your TV.
"it was working fine a couple of weeks ago" - what changed since then, if anything?
Did anybody fiddle with the settings on the TV? Most 1080p TVs have settings to 'improve' fast moving scenes (like sport) and sometimes these have a very detrimental effect on general picture quality. Check your TV settings. If possible, try it on a different TV.
I know you are reluctant to have to rebuild the box, but if you want to send it back, you should install the bog standard image before returning it, to avoid questions being asked. Because this is the case, I would be inclined to install a newly downloaded image on the box, in case there is a corruption in the version you downloaded or it might have got corrupted while on the box. If the new version auses the same problems, then go down the route of returning it for repair.
Note: I would only do minimum configuration on the new image, just enough to test it. DO NOT SAVE AND USE THE SETTINGS FROM YOUR CURRENT VERSION, in case they are bad and causing the problem.
1. Install the new image.
2. Set up the satellites.
3. Scan the satellite where you have the problem.
4. set up your CAMs.
5. test.
I would not enable any bouquets or EPG before testing. If the box works, then add required features, one at a time, and check that the box still works after adding each one.