asus z87-pro motherboard mining problem

Hallo everyone. I had long time buying my motherboar asus z87-pro snd i decided to start mining. I want to use 5-6 GPUs but my system (windows 10) in device mannager detect max 4 GPUs, of these open cl recognise only 3 GPUs. I try mining Zcash with Claymore zcash miner v.12.4. I have unstability even with these 3 GPUs, because miner run so 15 minutes and GPU on pcie x1 stop working and computer freeze. It's problem of pcie x1 slots not pcie x16.
I use powered pcie x1 to 16 risers, but yet i have plugged only 2 GPUs direct to pcie x16 slots.

I try everything, reinstaling windows 7,10, reinstaling amd driver, bios settings, exchange GPUs to different slots, but nothing. I heart, that installation of linux may help, but I'm not sure.
Please help if someone have same problem. Thanks.