Duplicate MAC address of two different X520-DA2 NICs

Hello,

my question is directed to Intel NIC developers - we (CDN77) are using your X520-DA2 cards in thousands of servers - we have discovered that two different X520-DA2 NICs we have in our network do use the SAME MAC address. Intel support told us, that these two network cards are DELL based (Based on the part number G18786-002 in the serial number, this is found to be a Dell OEM network card) 

The conflicting MAC is 00:1b:21:bc:32:15.

Is this something what can happen from time to time? It would be a real flaw in the design - this makes me think the duplicate MAC is caused by some Chinese copy of the genuine Intel NIC.

You can imagine what mess can this cause.

Thank you!