@CharlesAndre 

If the wireless connection is not stable, try the below modifications on the AX6000, then monitor:

For the 2.4GHz: choose security as WPA/WPA2- personal, Version:WPA2-personal, AES; Channel 11; channel width 20MHz;
For the 5GHz: choose security as WPA/WPA2- personal, Version:WPA2-personal, AES; Channel 44; channel width 40MHz. 

BTW, how many devices are connected to the AX6000 network, wired and wirelessly? What are they? Are all the wireless devices experiencing the same disconnect issue at the same time?

@Kevin_Z

thanks for the reply, I will make the changes and monitor,

When the problem happend, they all loose wifi connection in the same time , and when I look at the AX6000 network map dashboard, the number of Wifi connexion is at 0 and stay that way unless I reboot the router

regarding the type of Wifi devices I have: Ecobee thermostat, Nest cameras, Wemo switchs, sprinkler system (RainMachine/Android) iOS devices (ipad and iPhone), ChromeCasts device, some Google Home and some android  devices.

For the wired devices, laptops (Windows and Mac), Synology server, they never loose internet access while the problem occurs

So it's around 65 devices (lan and wireless)

@CharlesAndre 

Thank you very much for the details. Please try my previous suggestions then monitor.

BTW, as for those iOS devices, please try to disable the Private MAC address on those devices and see if it helps:
https://support.apple.com/en-us/HT211227