DIAGNOSIS You're experiencing interference or a channel conflict on the 5GHz band. It's a common setup issue, not hardware failure.
FIX Log into the router's web interface (router.asus.com) and change the 5GHz control channel.
- Go to Wireless > Professional tab for the 5GHz band.
- Set Control Channel to a fixed number (try 36, 40, 44, or 48).
- Apply settings. The router will reboot. This instantly fixes most random dropouts.
IF THAT DIDN'T WORK A firmware bug might be causing it. Go to Administration > Firmware Upgrade, check for updates, and install the latest official version. After updating, perform a full reset by holding the WPS button for 10 seconds while powered on, then reconfigure.
HEADS UP If you're using Smart Connect (band steering), disable it during troubleshooting. It can cause unstable client connections on this model. Set separate SSIDs for 2.4GHz and 5GHz networks.