@Alexandre. Unfortunately I am remote from him, so not easy for me to jump on his network. Though I guess I could VPN in using the NAS! Seems unlikely it is false positive from the NAS. It started...

@Alexandre. - yea, it puzzled me as well. I only have the one network, no Guest network. I figured I covered your possibility #2 by changing the IP address the Deco assigned the NAS, and sure enough...

@Alexandre. Good questions. Should have included more info. So the deco is in mesh mode. He is using a cable modem(not router). And the NAS is plugged into the main deco. And the deco is assigning...

I run my dad's network for him. He has a Synology NAS on the network that keeps reporting an IP conflict. I did just try to reserve a different IP address for it and sure enough it eventually...