Chosen Solution
The last week I’ve experienced a weird bug / glitch that I’m unsure of what is causing it. For my 16” MacBook Pro I got a BENQ PD2700Q monitor connected through a HDMI -> Apple USB-C Adapter -> MBP. The flicker I experience appears EXTREMELY quick and with no apparent pattern. I always notice it with my eye and had to record with my iPhone XS Max in slow motion to catch a picture of it. It does not appear at all on the built in 16” display, only on the external display. I made a GIF of the flicker seen here: https://imgur.com/EnEXKqn For clarification, marked in red here: https://imgur.com/gREjAyg
When recording that, the only thing I did just before (1 sec or less) is moving / clicking with my mouse. Looking at it frame by frame its gradually appears, becoming clearer, peaking and then fading. The laptop haven’t been moved since February since i’ve been working from home and I bought it in December. Its currently in perfect condition. So no physical damage that could have caused it. What info I got now: White, small horizontal lines appearing for a few ms.Seems to only happened on the left “half” of the monitor.Does only happened when Im using the computer, tried having it on idle / doing nothing without any flicker occurring.GPU & CPU temps are all stable and normal. Performance is as expected.No stuttering or performance degradation when it happens.No “pattern” to it, happens at random intervals but tend to be sometimes a 30 minutes wait between each time and this morning it hasn’t happened in 4 hours (So far). Seems to be triggered by activity on the display such as video playing, scrolling, playing video games (World of warcraft Classic, so not performance intensive).Resetting the NVRAM & SMC seems to fix it temporarily for a few hours / up towards a day.Refresh rate on both monitors is set to 60hz at default resolutionsWhen using only the built in display, I forced it to only use the high performance / dedicated GPU since I thought it could be related to it, no flicker.Used to have everything connected to the right side of the computer, 1x digital av adapter with power, hdmi + webcam connected through one usbc and next to it I had the usbc - USB adapter with my mouse. Currently only got HDMI connected to the AV adapter, power on left side ports. Software changes done recently: The only software change i’ve done is installing Citrix Receiver / Workspace to access Bloomberg Terminals from home (Had to reinstall it twice due to glitches)Disabled and later enabled the battery health management (to see max capacity with it turned off) Currently testing: Running at a slightly lower resolution (2048x1152)Cleaned the HDMI cable ends + ports on adapter and monitor with compressed air (Only got 1x cable + 1x hdmi port on the monitor).Running with True Tone, Night shift and automatic brightness adjustment disabled.Testing the display with my partners Early 2015 13” MBP (No DGPU), no flicker from what I have noticed (currently testing this) Have not tried: Reinstalling OSXNew HDMI Cable & Apple AV AdapterChecking monitor internals since I live next to the ocean (eastern Australia) so corrosion has happened on other electronics such as TV ports and the monitor is +2 years old with heavy daily usage. So salt water in the air could be a potential factor. HWINFO: BENQ PD2700Q Running at max res (2560x1440, default res)2.3Ghz, 8 Core I916gb DDR4 @ 2667Mhz5500M 8gbCatalina 10.15.6Some cheap bluetooth mouse from office works connected to the laptop through a usb-a receiver connected to a usb-c -> normal USB adapter from apple.Magic keyboard. If anyone has any idea on what could be the cause behind this I’m glad to hear :-). Cheers Note 1: Running on lower resolution seems to fix the flickering to some degree, I’ve been running it on the “one step lower” (2048x1152) resolution for 8+ hour without any flicker. I switched back to 2560x1440p (default) and the flicker has so far happened 3 times within 45 minutes.
Wow a very through write-up! I fear your system is the issue here. The data path of your video signal goes through a few steps before it gets to the USB-C port and onwards to your external display unlike your internal display (very short path). Its something in this pathway internally that’s messing you up. Let’s give this a try go into your Energy Saver preferences (you’ll need to unlock it) alter the Automatic graphics switching setting so your system is forced to use the discreet GPU only by unchecking it.
When you look at the About This Mac the GPU listed should be your AMD GPU. Did that alter things? Find out which graphics processor is in use on your MacBook Pro I haven’t tried this great utility on the newer MacBook Pro’s or Catalina (no 32bit support) so I’m not sure if it works gfxCardStatus which is a bit easier than always fumbling with the Energy Saver.
