Dell monitor goes black after switching HDMI 2.1 KVM inputs

Level1 Store KVM Helpdesk
1

KVM Model:

Dell monitor goes black after switching HDMI 2.1 KVM inputs

USB Interface (5-gigabit or 10-gigbit):

10 GB

Problem:

My setup includes:

  • MacBook Pro with Apple M5

  • MCT T6 USB-C docking station

  • Dell U2718Q monitor

  • MSI G273 monitor

  • The Mac is connected through the KVM/dock setup

The Dell works initially, but after switching the KVM to another computer and back, it often becomes black. macOS still detects the Dell as connected and reports it online. Unplugging/replugging the HDMI cable sometimes briefly restores the display, but the screen then goes black again. Power-cycling the Dell does not consistently help.

I have already:

  • Set the Dell to 60 Hz

  • Confirmed the monitor and HDMI cable work with other devices (other laptops and desktops)

  • Confirmed macOS still detects the monitor when the screen is black

  • Tested switching between KVM inputs

Could you advise which EDID procedure is correct for this model, whether there is a firmware update, and whether this could be a known macOS compatibility issue? If needed, I can provide photos, serial numbers, logs, or a short video of the failure.

Other Notes:

My MacBook is connected to a MCT T6 USB-C docking station, which my Work laptop also uses, there are some issues with my work laptop, but unplugging the docking station and replugging it fixes the issue 90% on the first try, and 100% on the second try. But the primary issue is unplugging and re-plugging my MacBook Pro doesn’t work in this case sadly. Thought this might help!

2

There are a few mac sleep events that can effect the ability to wake correctly. Some to try:

System Settings → Battery → Options
Turn on “Prevent automatic sleeping on power adapter when the display is off”

Another thing you might try is to just stop your laptop from using various sleep-related modes, but still allow the mac to put the display to sleep. Here are some commands commonly used to fix sleep/wake failures:

sudo pmset -a powernap 0
sudo pmset -a womp 0
sudo pmset -a tcpkeepalive 0
sudo pmset -a proximitywake 0
sudo pmset -a hibernatemode 0
sudo pmset -a autopoweroff 0
sudo pmset -a sleep 0
sudo pmset -a displaysleep 10

If you dislike any of these changes, you can always reset all of them with this command:
sudo pmset -a restoredefaults

The idea is to remove reasons for the Mac to wake or re-initialize the display, since that seems to be when the crash happens.

Important notes:

powernap – setting this to 0 will stop background updates, and syncing won’t happen while the Mac sleeps. It just catches up when you wake it.

womp – setting this to 0 will disable remote wake or other commands while the mac sleeps.

tcpkeepalive – setting this to 0 will disable things like find my on the device during sleep.

If you set the sleep command to 0, your device will never sleep.

Testing to conduct if there are issues:
Apply everything at once and see whether or not the panics stop. If they do, revert settings one at a time to find the one that matters, starting with sleep and displaysleep, since those are the most likely culprits.