I am experiencing the same issue. In my case, the router (AR300m16-ext) becomes unresponsive after about 3 days. It doesn’t matter if it has wireguard vpn turned on or not. My router has also stopped responding while in AP mode (not repeater).
One interesting thing is that the middle green LED light blinks sporadically and randomly when it is hung up and the amber wifi light turns solid. I noticed the middle green light begins to randomly blink a few hours before the router becomes unresponsive.
While the router is unresponsive, if I disconnect a client from the wifi signal, it is not able to reconnect until I restart the router by unplugging and plugging back in.