Please guys, help is greatly appreciated. I'm kind of desperate. To make it short here's a summary of my issue and new things I've checked.

Summary / Problem:
One hashboard is randomly disconnecting while mining, sometimes from boot up, sometimes happening after mining for a while. I can not tell that it's a specific board as each board works fine. Two boards at the same time work fine aswell two. The problem seems to occure when three boards are connected.

A while ago a fan failed - maybe it is common, Idk, it is my first asic. Now, about 2-3 months after the first fan failed, the second one failed aswell. There might be no corellation but I find it weird.

I supposed it could be the PSU and got a multimeter.
-PSU's voltage is 12.4V not being under load. As the second fan has just failed, I can't test in under load.
-Continuity test of PCI cables as well as female connectors at the hashboards seem okay.
-Electrical socket's grounding is good aswell.
-Voltage is stable at 240V out of the socket.

Do you think it could still be a PSU issue? Or rather Control board?