No segway, I've posted a bit of a discussion above. Not all that interesting unfortunately. The error message was obscure but the problem space was pretty small

No segway, I've posted a bit of a discussion above. Not all that interesting unfortunately. The error message was obscure but the problem space was pretty small so I did mostly the same thing as Fabian and searched online for related terms to PCIe hotplugging and PCIe address allocation.