DHCP not working properly, log filling with DHCP assignments

From reviewing my Wireshark logs that spanned the time when it was not working until it was working, the DHCP Offer messages have only ever come from the Orbi. Those messages actually have the IP address of the sender, which was always the Orbi. The other reasons I have a hard time believing it's another device is that once it starts working after I have reset DHCP one, two, three, or four times on the Orbi, then it stays working as long as I don't do anything that causes DHCP to reset again (in other words, don't mess with the router). If it were even sporadically the D-Link NVR-312L, I would expect the problem to be at least consistent - in other words, some random device not getting a good IP address on a relatively consistent frequency. I last had the problem yesterday evening, and after resetting DHCP three times I think, it started working and it has worked consistently ever since. I have made a specific point not to change *any* settings on my router since then, specifically to see if it stays stable.