Sleeping issue resolved

[pshufd]

I had a sleeping issue with my M1 Max Studio hooked up to 3 Dell Ultrasharp 27 inch 4k monitors. 2 U2718Qs and 1 U2720Q. There were two issues: the system would wake up all of the monitors and leave them on until the morning and the system wouldn't sleep automatically. I could manually put the system to sleep though. The system is used as the household NAS, but prior behavior is that the monitors would stay off.

I did some digging around and it appears that Bluetooth could be a factor so I turned it off and that solved the monitors coming on at night problem. But it didn't solve the issue with the system not automatically going to sleep.

Yesterday I replaced one of the U2718Q monitors with a U2723QE and it now sleeps the monitors and stays that way. I don't know if it was a monitor setting, the monitor, cable, devices charging off the monitor but it's nice that it is solved. The old U2718Q is now on my wife's new M1 mini and it sleeps fine on her system. So just some peculiar stuff where a change in hardware fixed it.

I've seen a lot of issues with Apple Silicon Macs, sleep and monitors and they can be rather frustrating but at least this is fixed for me.

 

[pshufd]

This problem came back a week later so I decided to spend an hour diagnosing it as it's one of those things that drives me nuts.

I unplugged all of the stuff from the hub and turned off USB charging when the monitor is in standby and this fixed it. I then added back one device (a microphone) and the problem returned. I suspect that there's a bug in the monitor firmware that results in it waking up and then waking up the Studio. The problem occurs with the U2720Q. It's not a problem with the U2718Q or the U2723QE which are the other two monitors on the system. It's not a problem as I can just move the keyboard, mouse and microphone to one of the monitors that doesn't have the problem.

It's possible that there's a firmware update that could fix the monitor but I'd probably have to hook it up to a Windows system to apply it. For now, it's just easier to use one of the other monitors.