I am experiencing flickering with my dual monitor setup. The nature of the flicker is "on/off", i.e. the screen gets completely black for a split second (sometimes a few seconds) and it goes back on. Sometimes it happens when I am not doing anything on that monitor, and sometimes it seems like it is triggered when pixels change on the monitor (opening something, or even just moving the mouse cursor)

I have a dual monitor set up at work with my MacBook Pro 13" 2017 (two thunderbolt 3 ports).

I am using the following to connect these monitors to my Mac:

  • BenQ BL2780T monitor
  • AOC I2475PXQU
  • Kensingon S4600P docking station
  • Belkin HDMI-USB-C adapter

The docking station connects to the MacBook via a thunderbolt 3 cable. The AOC monitor is connected directly to the docking with DisplayPort. The BenQ is then connected to the remaining Thunderbolt 3 port on my Mac via a HDMI-USB-C adapter. The docking station provides power to the Mac.

It seems random which monitor flickers; sometime it is the BenQ, other times it is the AOC. Also, it is random which port is involved in the flicker. However, I only see flickering when two monitors are connected at once.

I have also used a Satechi slim multiport (as a very simple docking station), and I see the same flickering behavior. I have tried different cables, and the issue persists.

I have also tried another AOC (same model) monitor together with the BenQ, and it still flickers.

I am going to try another MacBook Pro (same model) this week, and will report back.

Is this a software issue with High Sierra? Are the two monitors "incompatible" for some reason? I see no reason why the flickering happens. I really hope someone can help me out. It seems similar issues are common, but I have not yet found a common explanation to fix these things. Needless to say, I have tried the standard things, like various resets etc.

  • 1
    I have this exact issue with an OWC Thunderbolt 3 dock and an AOC and ASUS monitor setup. I've tried tons of cable configurations — hdmi to usbc, displayport to usbc, vga to mini dvi... same exact issues. The only way I'm able to resolve them is with a restart.
    – Jon
    May 19, 2018 at 21:33
  • Restart of what? Your computer? Surely that does not solve your flickering problem for good?
    – Yoda
    May 19, 2018 at 22:24
  • 1
    Yeah, sorry I should have clarified — restarting the computer after plugging it into the dock is the only thing that works for me, but it's only stable until the next time I disconnect. After re-connecting, I have to go through the restart cycle again to get rid of the flickering.
    – Jon
    May 20, 2018 at 2:04
  • When I plug in my external at home through my IOGEAR dock, I get no response from my monitor until I reboot. This isn't a problem with my Belkin dock at work. Aug 21, 2018 at 12:27
  • 1
    did anyone find a solution to this Issue? In my Case it is a USB-C to DVI (only this one is flickering) the other one is connected via an Active DP to HDMI Adapter and works fine.
    – bMalum
    Feb 18, 2019 at 10:34

3 Answers 3


Rebooting my MacBook with both monitors plugged in actually fixed the second monitor flickering issue. Yay.


Sounds to me like it might be an SMC issue - at least that’s one of the first things I would try - reset the SMC. Easy enough to do... https://support.apple.com/en-us/HT201295


Had this issue once - the solution is to make sure that all the monitors are set to the same refresh rate (Display Settings -> Advanced Display Settings).

In my case, I had 2 identical HD external monitors with the same refresh rate but not compatible with my laptop's which I was extending. I made sure both monitors were set to the same refresh rate and turned off the third (laptop's) monitor in the display settings.

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