You may want to consider getting your modem tested by your ISP. Also check out the possibility of modem faults. A modem reconfiguration or replacement could resolve the modem issue.
I use Wireless Network Watcher from nirsoft.net. My router is a Sagecomm 5260cv supplied by Optimum.
I have one device (NVR camera)that shows one ip address if I view the modem's list and a different ip address if I view the wireless network watcher screen.
This, and other weird issues have wreaked havoc with my system because I can't get the router to honor the static ip addresses. I'll declare something as 192.168.1.5 and after a power outage it might end up at .172.
Any suggestions or ideas are appreciated.

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