Ever since the latest firmware update (ASUS RT-AX58U Firmware version 3.0.0.4.388_25210), I have been experiencing dropouts a few times a day. I have emailed ASUS support.
It may help if you provide more information on how your router is configured, and what exactly is "dropping out". What exactly is dropping out; the WiFi, the WAN, the LAN? And it helps to list what troubleshooting steps you've already performed.