Ran that video on loop for a while. All signs are gone. YAY
Went and played like 40mins of Tobal 2.
The UI is back again.
Am I going to have to run a video like that after every time I play a game with static UI, or is the image retention something that can go away by itself?
Same thing happens on my LG 27MU67, 4K IPS monitor.
That image retention/after-flicker effect - which is temporary, so you don't have to run that video all the times, you just need to turn the monitor off and leave it for a while - is not caused by static graphic elements in general, but only by heavily flickering 480i objects. I posted about the same topic a couple of times, a few pages back.
Fighting Vipers and Virtua Fighter 2 on the Saturn do the same thing (they both sport an intense-flickering UI), but you can try and leave on pause for two hours any 240p Street Fighter game, for example, and nothing will happen.
It really looks like severe flicker puts the crystals of (some? All?) IPS displays under stress, and that's the result. I remember reading on Steam people freaking out about the very same issue, with Metal Gear Rising when running at interlaced resolutions on PC. Plus, as it's been mentioned as well, New 3DS XL's IPS screens suffer from it too, and you can trigger the very same occurrence by playing stuff like Galaxy Force II, which has parts of its UI which flicker at a very high frequency.
It's surely annoying, and so far I haven't managed to find a solution (I'm not even sure there's any).
Unfortunately, after having experienced IPS displays, I can't get back to TN panels either - I own a TN Asus too - even though they don't suffer from those problems at all... Especially with retro stuff, colors look so off on them, and the color shift in TATE mode is pretty much unbearable to me. :/