Please assist - weird issue with mining rig

Hi chaps and chapettes,

This post will be more for advice as I am currently out of ideas.

First a little bit of background.
My brother and I started mining last year. Earlier this year he wanted to start building his next rig.
It's a basic rig, the parts were as follows:
CPU: G3900
RAM: 1x 8gb Crucial module
Motherboard: Biostar TB250 (12pci-e)
Power supplies: 2x Corsair RM1000i
Nvidia GPU: 6x 1060
AMD GPU: 6x 570
Basic wooden frame.

Right, when he first got the board, he accidentally bent two cpu pins by dropping the protective cover on it.
He seemed to have fixed it with a needle and magnifying glass, luckily they weren't completely bent, just slightly.
Before he bent it back, I told him to just try running the rig with the bent pins, he might just be lucky and everything works.
He wasn't lucky and it wouldn't post.
So the next day he bent them back as close as he could. He sent a picture through and you couldn't tell which ones were bent.
After he bent them back, he ran a 1060 in the pci-e x16 lane to install OS and setup the rig.
It wouldn't post, but as soon as he had it on one of the other pci-e x1 slots via a riser it would work. Onboard graphics also worked.
He tested it with a different card, same result.
We then thought that it is the bent pins that caused it and he bought another motherboard, same model.
When that arrived he had the same result. Everything worked except the x16 lane.
We then updated the motherboard's bios, no difference. Cleared CMOS, no difference.
He sent the motherboard back. Ordered two x13 pci-e Asrock motherboards.
He then tested the first board with a RX570, same result. Then tested the second board, same result.

We then started troubleshooting to try and get to the root of the cause.
Things we tried:
Different PSU - same result.
Different ram module - same result.
Different power chord - same result.
The CPU being the only part he hasn't replaced yet would seem like the culprit then.

Is there anything else we can try before he orders another cpu. I know it looks like the cpu,
in all honesty I have never had bent pins myself so I don't know what to expect.
Is it possible that the pins messed up the cpu?

Thanks in advance