I have had some issues when playing new 4K UHD Blu Ray disks in my OPPO UDP-203.
I had been using a old Samsung BD player with a Samsung Q6 TV. I recently replaced the Q6 with an LG C4 and replaced the Samsung BD player with a UDP-203 (the OPPO had been in a different system with a Q80 TV, but I rarely used it so I decided to swap the BD players between the 2 systems when I got the C4).
Most 4K disks play fine in the OPPO/C4 (better than fine, actually more like sublime). However, some 4K disks generate an image that is almost completely bright blue blocks. For example, in the opening scene of Bladerunner (Final Cut) it is barely possible to make out the outlines of the buildings or anything else. The text in the opening credits is also highly distorted with streaks of green. I had a similar issue with one of the Star Trek 4K triliogy disks I bought recently, but one of the other 4K disks from the triliogy was fine (I can't remember offhand which was okay and which wasn't).
The Bladerunner disk played fine in the old Samsung BD/Q6 combo. Thus, I suspect the UDP-203 is having problems with the format of some of the newer 4K disks, but I can't rule out a compatibility issue with C4/OPPO combination. The firmware on the OPPO has not been updated in years, so I'm going to try updating the firmware. It looks like the last firmware update was in 2019 so I might be SOL if that's the problem.
I'll probably try connecting the old Samy BD player to the C4 to see if that works.
Any other ideas/suggestions?