So this is my final obstacle ...
i got 4 cards connected with raisers on PCI-E slots 1,2,3,5 (if looking from the left) (gigabyte GTX 1080 TI)
the other 3 available slots do not get the card detected (not even as a question mark in device manager)
i swapped slots, i swapped raisers - all working fine, this is happening with different GPUs in different Raisers.
Slot 04 is never working. not even if one GPU is connected to it.
what i did so far: Enabled G4, set all to Gen1 (that solved other issues that i had and allowed 4 gpu's), disabled all onboard USB except for one (need it for Wireless)
i`m getting really frustrated (enough to buy a different MB).
so anyone has a solution, or a suggestion on a 100% working MB that will allow 6 GPUs without tweaking and messing around with it - i will be very thankful