S2721DGF, crashes but is possibly NOT defective

I read a thread talking about S2721DGF crashing, ended up exchanged for a new unit. My unit seems to work perfectly except there is some situation where it crashes. I am not sure what causes it. In my setup I have a high quality 5m DisplayPort-DisplayPort cable, no other monitors. Something happens and now the screen remains black. Pressing the on/off switch does turn the power LED on/off, but screen remains dead. As soon as power cable is removed and put back in, the splash screen appears and monitor starts working normally.

Possible situations where it happens: after computer sleep, after doing something with Remote Desktop Connection, ClickMonitorDDC's power off (which is a special state, but also that should always fully turn power back on when physically pressing the switch off>on). The screen is often in this dead state in the morning when I try to use it. Computer is running, but no image no matter what. However, power cable out and in, and it works again. I tried fiddling around but I couldn't pinpoint the situation where the problem happens.

I had exactly similar problem with my previous Dell U2713HM, only power cable out/in would revive. I don't know exactly what caused the problem in that case either, but then I used a different older DisplayPort-DisplayPort cable (older than my current v1.4 cable).

How come these Dells crash like this? Please Dell, fix the monitor firmware so that physical power off/on always resets whatever the problem is? (I tried finding Dell support email for this, but apparently there is none.)