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 messed up the 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.

*** Update ***

I finally managed to get ahold of several humans in the online chat tool.  Initially this seemed promising, but now I'm just frustrated and am at the point where I have little to no confidence in anything any of them say.  The 1st person confirmed my problem sounded like a similar issue that others have had, and that it might be due to the fact that my router is > 2 years old.  He claimed that sometimes routers develop issues with IP routing after 2 years...  Sounds like BS to me, but whatever.  He had me swap out the router for a new one.  This was yesterday afternoon.  By yesterday evening, the problems are back so I got online with another support human.  After trying to completely restart the troubleshooting process (turn everyone off/on again, etc), he said he escalated to an "advanced technical team" and asked for my contact info, which I gave.  I wasn't sure what to expect next, as he didn't give me any details, so 20 mins later I pinged to ask if there was an ETA for when I would hear from the advanced technical team person.  At that point, a new support person responded and, basically, wanted to restart the entire troubleshooting process from the beginning.  Fast forward to this morning.  I asked for a status update, as well as for a ticket number.  I got a new support person who gave me the ticket number and, eventually, he said that this was going to require someone to come to my house.  I asked when that would happen and he told me somewhere from 10-noon today.  It's 10:36am now and I've not heard from anyone, although someone did remotely reboot the router again about 20 mins ago.  I'm sincerely hoping a tech person is going to show up but I don't have confidence.  I just checked the https://www.xfinity.com/support/ page, and it says I don't have a support ticket, despite what I was told by the support person earlier this morning...

Support tickets