No, I have a Camera Link PCIE card that causes any system I put it into not to boot. So it could be the card. But also, AMD firmware is...interesting... based on my experiences with Epyc motherboards.

Not really; link training and initialization for PCIe devices is really complex. A lot of motherboard bootware, even from reputable vendors, tends to handle obscure conditions by simply rebooting or locking up.

I wouldn't be surprised if there were certain steps where they simply forgot to include any sort of timeout, meaning the device can hang the boot process by simply not responding at the right moment.