I would update to the latest stable firmware. You're using a really old version. I don't know if that will solve your problem, but it's worth a try.
https://rog.asus.com/us/networking/rog-rapture-gt-ax6000-model/helpdesk_bios/
You can download new firmware here ... its German Asus website - https://www.asus.com/de/networking-iot-servers/wifi-routers/asus-wifi-routers/rt-ax86u/helpdesk_bios?model2Name=RT-AX86U
Direct path -...