Sometimes our Internet service (terrestrial wireless funneled through our router to all devices in our house) temporarily stops working, but comes back up within minutes. During and after the outage our Windows and Android devices never report a problem with the WiFi password, just network issues, and never require the password to be re-entered to re-establish connectivity.
On the other hand, our iPad Air 2 (Version 11.2.6 (15D100) Model MH182LL/A) frequently requires the user to re-enter the WiFi password, on some occasions many times. This despite the fact that the Internet interruption has nothing to do with the WiFi password. Once I "Reset Network Settings" on the iPad, and naturally I expected to have to enter the WiFi password once more, but as before I must enter it again and again.
The router is an ASUS RT-N66R and I have changed little of its defaults other than of course the password, but I changed the password shortly after buying the router and haven't changed it since.
How can we avoid having to re-enter the WiFi password on the iPad every time there is some kind of Internet interruption?