MAC Address Changing

I'm wondering if anyone else has seen an instance where the MAC of the printer randomly changes over to an unknown MAC. We typically see the 0021.b7xx.xxxx MAC on the port, but recently when deploying dot1x to our ports we noted where Lexmark printers (MS510dn, MS811, MX911) are connected, a MAC of eeee.3eee.xxxx will appear and the port will issue a dot1x failure, disabling the port. The MAC will revert back to the Lexmark MAC of 0021.b7xx.xxxx and everything is good. Just wondering what would cause this.