New Mini M4 Pro install - flickering monitor after 15.3.1 update

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I installed a new Mini M4 Pro yesterday. Everything ran great until I updated it to 15.3.1. Then the main display (27" Dell running at 2560x1440) started lightly flickering in the top third of the screen, but not the 24" Dell secondary screen. Swapped between the HDMI port and Thunderbolt, tried swapping dongles (both Dell's have DVI out). It's still happening. I didn't have an extra monitor on site to check if it was the hardware, but the timing with the OS upgrade was very specific.

The next step is to bring a different monitor for testing, and then if that shows flickering, downgrade to an earlier Sequoia.

Thoughts?

 

[Kenny99]

Have you looked at what Frequency (60 Hz or 120 HZ) you are running the monitor at? Try changing the screen resolution.

 

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Yes, we tried changing the resolution/frequency. It didn’t change the flicker.

 

[Mrbobb]

Once I fixed a flickering prob by changing from 59.95 to 60hz, go figure.

Also sometimes using a different display port may make a difference.

 

[Fishrrman]

I don't have "the answer" for you.

But the "flickering" issue seems related to either refresh rates, or the type of "color input"
in use.

By that, I mean (again, not an expert here), if you go into the display's menus, you may find a choice between "RGB" and "YCbCr" (or something like that).

If I'm not mistaken, the Mini (as well as MacBook Pros) will by default try sending YCbCr instead of RGB.

Sometimes the displays deal with that without problems, but if they get "mixed up", you can start getting that "out-of-synch" fast-flickering.

Sometimes changing the cabling schemes overcomes this.

Is DVI the ONLY connection method available to you?
Do the displays have any other inputs?

One other thing:
There is a way to "force" the Mac into recognizing a display as [only?] an RGB monitor. The idea is to coax the Mac into sending only an RGB color signal "out" to the display.

It used to be easy to set up.
With the coming of the m-series Macs, however, it's more involved.
But it still can be done, I believe.