0.8.5 can't change MAC address

I'm trying to troubleshoot someone's 0.8.5 that they couldn't get to see on their network. I have it hooked up to my network, and I have changed the MAC address in config.g, but it seemingly doesn't take effect. When it connects, it messes up the IP address for my other duet (that has the default beefdeadfeed mac). When I disconnect my duet that works, connect the problem duet, it shows up with an IP address that I did not configure and with the old beefdeadfeed MAC instead of the one I configured.

Any ideas? It's running firmware 1.15 beta 3 (early august)

Please share your config.g file.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Unfortunately the board is no longer in my possession. Which aspects were you curious about? I know pretty well what was in it, so I can provide that to you.

I tried several things from DHCP, to assigning a static IP, etc. I came to the conclusion (after making this post last night) that the SD card might not be getting read properly. The suspect duet has never been used, so we have had no way to ever verify if the SD card is being read. I'm going to get the person to try a new sd card and see if it works. It's odd, because the SD card can be read and written from and to by a windows PC.