Dual monitors on mac mini 2018 do not turn ON reliable

Thanks for all the suggestions.

After days of trying and testing this does not seem to work. I can not drive 2 x LG 4K 24UD58 4K from the TB3 interfaces.

The behaviour is totally random (display #1 works or display #2 works) and the same thing happens when waking from sleep.

Most intriguing is that during the boot phase you see the Apple on one monitor than the logon prompt on the other monitor and the first monitor than goes into standby and powers off (no signal). And totally random !

Anyway, I gave up, plugged a HDMI v2 cable in the mini and one of the monitors and everything works as it should. Both monitors turn ON and OFF as they should including when sleeping the mini.

This does seem to make a difference. I mean, when I choose 2 different TB ports, it seems to bring both screens up during bootup much more frequently (at least 50% of all cases). The feeling is that when I do a NVRAM/PRAM reset it seems to go back to only 1 out of 10 boots both monitors come ON.

Hi den.thed. No need to apologise of course. Sleeping my Mac mini is what I currently do. As long as the temperature stays below 50 centigrade I do not believe it has a negative impact on longevity.

But, I am not amused with Apple in recent years (price-point versus issues).

I did not found a solution, I am using a work around.

Thanks for all the suggestions so I did not miss the obvious :-) !

Thanks for your suggestion. LG Dual Controller is not applicable here at all. I have not tried this one.

I have installed On-Screen Controller v3.28 and played with it earlier this week. It does not help. I think it also run after the OS is loaded and does not help with the detection phase.

But thanks for the suggestion.

I've tried that several times. I have tried that again today. Makes no difference (my feeling is that it even makes things worse) and it is a difficult procedure. Let met explain : when I shut down the Mac, the monitors go into "no signal" mode within 3 seconds and go into "standby" 5 seconds later. So it is difficult to keep the monitors ON during the boot process. What I did not tell before and is quite interesting is that during the boot-up sequence, I often get the apple symbol on monitor #1, than monitor #1 switches off and the logon prompt appears on monitor #2 and monitor #1 stays OFF unless I unplug and plugin the video cable.

I did not know of the game mode which was ON, now OFF. Makes no difference.

SmartEnergy/Automatic standby : is not an option on this monitor model

Freesync / Displayport : tried, does not make a difference.

Monitor power button ON/OFF sometimes work, sometimes does not.

Both monitors are set to SMART ENERGIE SAVING = OFF and AUTOMATIC STANDBY = OFF. And monitors have been reset dozens of times. Having said that, I think that the monitors quick power-OFF might be very well the root cause of the issue.