Hello,
Thanks for quick reply, now I know my options!
I'll check the firmware version just to be sure later on, but I think it was 6.xx, so it's rather the case of faulty hardware.
There's one thing, I read the KB article and in my case CPU LED wasn't lit at all, only the Group LEDs and 1/4 of Port LEDs and they were solid green.
And I'm not sure if I can submit RMA, as this device is part of my private rack used for learning&testing.
Maciej