Hello,
Forgive me for the intrusion, but what does LENOVO say about your problem and the use of the generic ESXi product image instead of the custom one released by the manufacturer itself, in this is right in my opinion. And don't even rule out that the firmware is irrelevant, the manufacturer doesn't release several updates over time for no apparent reason.
If you want to reach a solution, in my opinion it would be better to start by involving the manufacturer of those systems, which are not very common objects, and follow the instructions they may provide you.
Regards,
Ferdinando