Were both addresses in the range of addresses assigned by your DHCP server?
This should not happen, but I'm just curious if it is possible one ipaddr is for wired and one for wireless?
I have a Roku Ultra that I set up to use the wired network and now it is using the wireless network and has two ip address (192.168.1.248 + 192.168.1.249) with the same MAC (D8:31:34:5B:AB:36). At some time I must have also had a wireless connection setup since the Roku device is now setup using the wireless network connection. I did not make he change from wired to wireless network connection on the Roku device.