After long-running problems where my Mac mini (Late 2012 unibody) won't wake up from sleep, I started running
caffeinate -s. But even this doesn't fix it. My Mac claims to still be running, flickering lights on my external hard drive, etc., but the monitor is asleep and says there is no signal.
My only options are to hard-boot, or weirdly to turn the hard drive off and on. This brings the monitor back awake "the Mac will shortly restart".
What can be going on? Is something sleeping and failing to wake? Is my Mac just dying? Is my DP-based monitor trying to be too smart? It's a Dell U2715H.