I have a Monoprice Voxel (rebranded FF A3), and I have the exact same issue. I bought the Voxel in Jan 2020, but it keeps changing the MAC address on reboot! I would like to assign a fixed IP address (from DHCP pool) to the fixed MAC address.

Any help to get the firmware upgrade? I might try contacting FF to see if they will help.

I have sent you a private message as well.