It is very easy to open the OPPO including the drive (only some small screws holding the top cover of the drive) and I suggest that you take a peek from time to time - longer hairs within the disc transport could cause damage to the drive as it has lots of moving parts.
Then you are one of the few persons who know. The ringing that is introduced by 1080p to 2160p/4k upscaling will of course always give an impression of added sharpness although it is really an artefact. I have seen a number of Panasonic players and they are usually set to sharpness zero which...
From what I have seen all OPPO, Sony and Samsung players employ no sharpening with sharpness set to zero while Panasonic is still employing sharpening at the zero sharpness setting so they require a negative sharpness setting in order not to introduce artificial sharpness. I seem to remember it...
I like to go to 70mm festivals which means I have not watched many of these movies at home for about 15 years. So for me I have not watched my 4k versions of Lawrence of Arabia, Spartacus and West Side Story nor the previous Blu-ray versions. There are others but these three I have watched 4, 5...