Are you using original or modded bios for those vga cards ?
What program u using for overclocking ?
Are u usng powered risers ?
The cards hashing fine without any overclocking ?
PSU wattage ? Psu can provide enough power for six cards and your mobo/cpu...
Full system spec can be helpful ...
If modded , flashed bios , then flash back the original bios and give a try again
If the vga cards have a original bios , then use DDU , remove the installed driver
- Download the driver from amd website
https://support.amd.com/en-us/download/desktop?os=Windows+10+-+64- Uninstal Driver , DDU link :
http://www.wagnardsoft.com/forums/viewtopic.php?f=5&t=788- Install the downloaded driver , if you are going to install the driver when all 6 cards plugged in , then make sure , you not going to turn off the pc during the driver installation , it might take 15-20 minutes , the screen might going black or flickering during this time .
- Disable win 10 automatic driver update for your vga cards , How link :
https://www.groovypost.com/howto/prevent-automatic-driver-installation-in-windows-10/- make sure your monitor is connected to one of your vga cards , not to the onboard graphics