Connectivity issues since Tues

Devices on my home network have been having connectivity issues since Tue.  Rebooting the devices does not help.  Rebooting the router does help, but only for a short/random period of time and then the devices lose connectivity again.  The router appears to be handing out duplicate DHCP IPs and also seems to have [Edited: "Language"] up Reserved IP settings for some devices (e.g. 2+ years ago ago I assigned some devices Reserved IPs and now they no longer have them.  Additionally, other random devices ARE listed as having Reserved IPs - and these are devices that I can guarantee were NEVER assigned a Reserved IP - e.g. the IPhone from a construction person who's building a patio cover in my backyard.)

I had originally included a ton of info in this message, but it the page refreshed when I added a Tag to the post and I lost it all and I don't feel like spending another 30 mins rewriting everything.  In any case, the reason I think the router is sending out duplicate IPs is because ipconfig /all is reporting that:

  IPv4 Address. . . . . . . . . . . : 10.0.0.20(Duplicate)

If you need any more info, please let me know.  BTW, I also tried using the support assistant thing, but it doesn't appear to work.  I asked a question 45 mins ago, and it appears to still be thinking on how to reply.  I can't cancel/retry that, so I decided to make this post.