AO on the display, indicates that the system has started correctly as does the beep (which is actually one short beep) in your video.
POST/BOOT issues with your rig could be due to many things, but the first thing to check would be your SSD('s).
How old are they?
What kind of memory chips they are using?
Also is the firmware on them, up-to-date?
The SSD is new, it's a Samsung EVO 850. And the memory is also new, couple of months old. G.Skill F3-2133C9D-16GTX. The firmware on the SSD is up-to-date.
I'm pretty sure the 'beep' was shorter before. The one in the video is like a full second plus.
But as I said in my first post, it doesn't bother me much having a longer beep: the computer still boots and runs just fine. The problem is that once a week or so, the computer will boot with the normal short beep it did before --and fail. It will then go on a boot loop (two or three times) until it boots with a long-er beep. And that worries me.
I only have a small OC in the CPU (4.1Ghz) and the memory at 1866Mhz. I will now try to run the computer with no OC at all, and the memory down to 1600Mhz, and see if I still get a random boot loop.