MacMini external display goes black intermittently

I have a 2018 macmini, and it runs great apart from one thing. After having used the computer, sometimes for several hours, and sometimes just a few minutes, my external display (a BenQ EW3270U) goes black for about 5 seconds, then goes back on. All is then normal for a few minutes, and then the 5 second blackout happens again. This goes on until I do something about it. Sometimes unplugging and replugging the display cable solves it for a while. Sometimes a reboot is needed. But the problem always returns. This is with regular use, just using the web and emailing for example.

I also tried the NVRAM and PRAM resets, but the problem persists.

Does anyone recognize this problem, and/or know a solution for it?

Is it likely that using an eGPU (which I might want to do also for other reasons) would solve this?

Is it possible it’s a physical connector problem?

Unfortunately not. This happens with usb-c to usb-c and hdmi to hdmi. So different cables and different ports, but still happens.

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I’ve not seen this particular failure mode, but black screens from my 2018 Mac mini are no stranger. In my case, it tends to happen after a reboot, particularly if the screen goes into power-save before the Mac is ready to detect it.

Not much help, sorry, but I don’t think you can rule out the computer/OS itself being dodgy. I’ve also come across multiple other people with the same problem as mine.

I had a similar problem on a Mac Mini where it wouldn’t wake from sleep.turns out an app i was using had a memory leak and would end up with a massive swap file, seemed to leave no room for RAM for the video card.

I could still vnc onto the machine and all was still good, just no output to the attached monitor.

I have had that exact problem with a MacBook Pro, but this is different.

Yes, I have a (very vague, and layman) feeling that memory usage may have to do with it.

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My Mac mini has also been having intermittent display problems. Apparently a lot of people have since upgrading to Big Sur. Based on what I’ve read online, it started with v11.1 and got worse with v11.2.

This morning my monitor went out and for a while it didn’t look like I was going to get it working again. I swapped cables, tried a different monitor, etc. I was close to throwing the mini out the window and placing an order with Dell.

AFAIK, everyone has a theory and absolutely no one has a solution.

I had the issue when I was running Catalina. I removed the External Graphics Puck, I changed ports and cables, and still could not get it.

I went through a lot of diagnosis hoops with Apple which did not identify the problem - During one round they have asked is about any beta software running. I did have a beta of Big Sur installed on an external SSD which may have caused an irreversible update to firmware.

I took it to Apple store and after a round of diagnostics they ended updating a complete reset of the system which appears to have cured the firmware update.

I have a M1 mac mini with the exact same monitor. Never had any issues until I got a replacement for my monitor which had a vertical line with no colours in it. Works fine with the FIreTV stick that is connected to the replacement monitor. I tried switching the ports and thought of trying the Type-C cable but got lazy. I used the same Mac mini with my older Samsung 1080p monitor and it looks fine. Switched to the Samsung as it is really getting irritating with the intermittent blank issue. I requested a replacement and will have to see what happens. If there’s any solution please let me know.

M1 Mini with two 32" monitors here. Whichever monitor was on the USB-C port would black out for several seconds at random intervals. Tried different cables, cable with dongle, and eventually had the Mini’s motherboard replaced. None of this solved the problem.
Finally invested in a high-quality (VESA-certified) TB-DP cable, and voilá: problem solved. I think a hefty, well-shielded cable will be the fix for most people.