5th card crash the system

Hi people,

I have a rig with
H97 anniversary
4 x RX 480
4 Gb ram
4 PCI-e riser Molex
Windows 10
120 EVGA PSU

Everything works fine from a month ago. The problem comes when I have tried to install today a 5th card.

I bought 4 of these crappy risers: https://www.amazon.co.uk/gp/product/B01ER2Z1GY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Only one of those risers can make gpu can be detected and powered. The rest of them I think they are broken.

After switch on my pc, sometimes pc shows a black window, system crash, and sometimes I can enter to Windows 10. In Windows 10, sometimes PC crashes becasue the driver. One time, everything looked good. I started Claymore but it said one gpu couldn't create a dag. So It doesn't help. In some thread, someone said try to put a bigger ram size. I tried with a 8Gb ram and it can create a DAG file but one of the GPUs starts to work at shitty ratio (9mh/s for a RX 480) until system fails.

I tried to change BIOS PCI to GEN1, doesn't help.

I spent a lot of time testing and waiting for systems recovery from failures. I'm exhausted.

Am I missing something?

I checked gpus are ok and works ok alone. I'm waiting for new risers I ordered from China and It will take some time to arrive