Apple

I had a similar problem with my last monitor (with a Windows PC.) It would randomly flicker vertical lines, and those lines would show a “ghost image” of something that was on screen when it started. I think it had to do with its variable refresh rate, as it often seemed to happen after gaming or tabbing from full screen to the desktop. But I could never find a reliable way to replicate the bug.

I could always temporarily fix it by running a “stuck pixel” video in full screen for 10-15 mins, like this: (seizure warning) https://youtu.be/-2eQhhMvi-U

It wasn’t really “stuck pixels” but it seemed to blast the problem away for some reason. Could’ve been coincidence though.

If it’s a variable refresh rate issue between the Mac and monitor, you could also try turning Adaptive Sync off if you don’t need it: https://support.apple.com/en-us/102144 And also disable it in your monitor’s onboard settings if you do turn it off or already have it off.

I went through a few different GPUs over the years with that same buggy monitor, including the GPU I have now. I since upgraded to a new monitor, and this one has not had any problems in the 6+ months of using.

So I’d hazard a guess that it’s the monitor. Try the pixel video if it happens again or messing with Adaptive Sync. If it doesn’t work, try other similar videos. Maybe it will help.

I have an M3 Max that does this, but only when I plug in two monitors at once over Thunderbolt. It doesn’t always happen either, haven’t figured out exactly what is causing it. I know my M1 is only capable of a single external monitor, so part of my suspects their multi monitor support is just poorly implemented over the latest TB spec.

Using M1 with a thunderbolt dock doesn’t do it, so I know it’s not the monitor. Plus switching out one monitor for another doesn’t fix it.

In the past to debug this problem I’ve used BetterDisplay

Don’t want to send up a flare unnecessarily, but I used to see that patterning on machines with dead logic boards.

My last 17” MBP did that shortly before the board died completely & left me s.o.l. If you’re still under warranty or AC, maybe worth getting it checked?

I am not certain if this would be an issue with M-Series machines. If anyone knows for sure, I’d appreciate any info.

Mine so far has had no issues like this. I have one monitor connected straight into the HDMI port and another monitor via a Dell dock (from work).

What is your resolution and refresh rate set to? MacOS can be quite picky.