I've got a 2018-version Mini, maybe about a month or so old, with the UHD 630 graphics. I swapped the default memory with 64gb of Crucial on the first day. I've got the Thunderbolt LG 5k screen on it and a Dell P2415Q on the HDMI port. For the first few weeks I've had zero issues. About a week ago, there would very occasionally be artifacts left behind by dragging windows around on the 5k, or random pixels showing the wrong color, always on the portions specific to MacOS like the title bar, raise/lower buttons, etc. Not too often, but the occurrences seemed to be increasing, and then more recently, parts of the screen flickering. Yesterday it was a column several inches wide about half way between center and right edge. Sometimes a reboot resolves the issue. Sometimes dragging other content into the affected area resolves it.
Today revealed something far worse than the other behavior. Portions of the screen were preserved and visible after locking, after resuming from sleep, and even after a full power removal / reboot. Not in normal quality, but enough to read what was there. I thought this has to be the monitor, but I swapped it over to my MBPr 16 and the image was exactly what it should have been from the laptop. Moved it back to the Mini and the previous image data was still there.
So, it is not the LG 5k. It also doesn't happen on the HDMI monitor. Could it be faulty video hardware in the Mini?
Today revealed something far worse than the other behavior. Portions of the screen were preserved and visible after locking, after resuming from sleep, and even after a full power removal / reboot. Not in normal quality, but enough to read what was there. I thought this has to be the monitor, but I swapped it over to my MBPr 16 and the image was exactly what it should have been from the laptop. Moved it back to the Mini and the previous image data was still there.
So, it is not the LG 5k. It also doesn't happen on the HDMI monitor. Could it be faulty video hardware in the Mini?
