We got this Archer C5400 almost a year ago (in fact, it will be exactly one year next weekend), and it's been fine most of that time.  However, in the last week or two, it's been having problems.  About once per day, the wifi (both 2.4 and 5 GHz) completely drops out.  Sometimes, the network is still there in the sense that devices remain connected, but there is no communication from one device to another or to the outside internet.  More often, the network drops completely and devices just report that they're not connected to anything.

When this happens, the wired connections continue to work correctly, but if I use a my wired desktop to get to the router's admin page, the page responds very slowly (if at all).  If the page loads enough that I can trigger a reboot, that usually solves the problem. If not, then I need to physically unplug and replug the router to get it going again.  And once it is back up and running, everything seems to work correctly for about 24 hours and then it drops again and the cycle repeats.

FWIW, the router is operating strictly as a router (not an AP), and is connected to a Motorola Surfboard cable modem.

Anyone run into this before?  I haven't been able to find anything on it