Losing Ability to Connect to Interface

Everything is fine after a reboot, but within a day or two when I click on "Attached Devices", instead of showing the attached devices that area of the page shows some sort of error.  The next thing to happen within another day or two is I lose the ability to connect to the interace at all.  All devices that I have stay working even when this happens.

I have tried a reset and there is no change in this behavior.

Up until 6 months ago I shut down my modem and router each night so they started each day with a fresh boot.  I now have a couple devices that need 24 hour internet access so they now stay on 24 X 7.  The number of devices that are connected have crept up to around a dozen.

Is something wrong with the router or am I just asking too much for such an old device?

If the latter, any suggestions for a replacement?  I am overwhelmed by the selection out there.

Thanks