Unfortunately such level of granularity is not available for home router devices. A simple firewall before you router can achieve the goal.

That's the administrative password for accessing the WebGUI of the router (not your wi-fi password). If you didn't change it throughout the initial setup of the router, it should be "admin"

The other thing you could try is to lower wireless transmission power to medium or low for both bands and see if any difference.

@Keeba Yes, that is it. You can save them as local file , there's a button on the bottom of that page "Save as". Then you can uploaad the file in the thread (not copy/paste, but attach). Meanwhile...

If anyone with AX50 shares the temp characteristics will be useful indeed, anything in the router logs, during these events ?

@sajiddude That means you are not receiving an IP address from the router's DHCP server. Here's a thread to follow if you want to try the TFTP method.