My Archer C5400X is on a battery-backup surge protected power strip. We had a power outage yesterday and when the power came back on, my wifi range dropped to about 10 ft. Previously it could hit the entire house with 5G or 2.4G. I have tried enabling each of the 3 bands independently, or using smart connect, with transmit power on high, medium, and low with no change. There are no other WIFI routers for hundreds of feet in any direction. The wired devices work fine. Usually I will see the network as having good signal throughout the house, but it will not connect unless I'm less than 10 ft away. I tried doing a factory reset and then all of these things again, same issue.