MacBook Pro M1 Pro issue with dual display after updating to macOS Sequoia 15.1

Same problem here on an M1 MacBook Air. It's not all monitors though. It's just my 4K monitor that keeps disconnecting and reconnecting. My two 2.5K monitors seem to be fine.

Really frustrating as my 4K drawing tablet is now useless until this is fixed.

I was having this issue running 3 external 4K monitors through an "iVANKY FusionDock Max 1" dock and routed through an HDMI KVM. At first, I thought my issues were due to my Thunderbolt to HDMI cables or my KVM setup.

I tried multiple fixes, but ultimately, the problem was only solved after switching to the Apple 1M Thunderbolt 5 pro cables between my dock and my M3 MBP instead of the cables that came with the dock.

Apple definitely needs to develop a software fix, but for those dependent on external monitors, this might be an (expensive) workaround.

I tried other cables, even those marketed as Thunderbolt 4 and 100GB USB-C, and even reverted to MacOS 14.7 for a while; this was the only fix that worked for me while running MacOS 15.1.

First of all, you need an image. This can be downloaded from several websites - Sorry, I am on iPhone here and can’t post the links that you will find them if you really want to

Download the.PKG installer

Then install it and from your applications folder using terminal (there are scripts around, it’s not too hard but it takes a while, I almost aborted due to missing progress…), you can create a USB boot, medium

Be sure to have a time machine back up that was made on 15.0.1 otherwise it won’t work

Then reboot your Mac holding The startup key and boot Into options

Repartition Your hard drive. (completely delete)

After that reboot or select your USB boot medium and install Sequoia 15.0.1

Now you can use your Time Machine back up to restore your Mac. If you don’t have one, you have a Mac on factory settings now

So much for an ultra short info, that worked for me

Same issue here..... MacBook Pro M1, external screen Philips Widescreen....... Really I got a 2nd MacBook for work... but if I had that updated.. I really had a issue. Why does it take so long to fix.....

I have one 'dumb' workaround that all of you could try.

While connecting an iPad via Sidecar, the HDMI display comes to live, but stops working the moment

the iPad is taken offline.

This is not a solution, but at least proof that nothing is wrong with the display, port or cable.

Rather something totally borked with how the display is detected.

Ok, so I have done some massive re-plugging of cables and I may have found something, that can help some of you.

My Setup:

M1 Pro MBP 14" + Anker TB4 Dock + Dell 4k + LG 2k screen (240Hz)

I have removed all HDMI Cables from the setup and I connected the LG Screen via DP to DP Cable to Anker Dock. The Dell Screen is connected with DP to USB-C cable to the dock. Here is the interesting part:

When I connect both displays to the dock and then connect the MacBook, the Dell screen (connected with DP to USB-C to Anker Dock) keeps turning on and off every few seconds. The LG Screen is fine and it shows 144Hz Refresh rate.

When I unplug the dell screen from the Dock and THEN connect MBP to the dock, then the LG Screen shows 240Hz rate and it still works fine. Then I connect Dell screen to the dock and it almost never flickers. Maybe 1-2h per hour. AND the LG Screen works with 240Hz still.

So, connecting the MBP first, then plugging the dell display might alleviate some issues until the update is out.

Hope this helps!

• correction: iOS 15

I have the same problem with an HDMI to USB-C adapter. It worked fine before 15.1 but now I can't use my external display. Does anyone find a solution ?

ZiaDaisy wrote:

• correction: iOS 15

Correction: macOS 15. iOS is the operating system used by the iPhone.

Have the same issue in Macbook M1 pro in 15.1 with LG ultrafine 21,5” 4k. Randomly the monitor connects and disconnects many times during the day.

It didn't work for me either. Strange that I left the screen still with Lungo and nothing happened. When I started working more, the blinking started... Soooooo annoying...

Yes, I'm using Macbook Air M1 with LG 29 inch FHD + 21:9 monitor with Thunderbolt cable(for display) . After i updated to 15.1 immidiently ran into the same issue.

this must be fixed by Apple.

I have the same problem with MacBook Air M2

Updated to B3 e issue still continues...

No. Actually worse for me--now it won't connect at all. It's crazy!