I believe I have found one resolution to this annoying issue. I work from home and I use the guest Wi-Fi for my VPN connection to the office.
I found the problem was being caused when the 1st guest wi-fi slot was enabled (either 5GHz or 2.4GHz). I deleted the 1st guest wi-fi and enabled the 2nd and 3rd wi-fi slots. All wi-fi connections are now stable and continue to be stable for well over a week. I tried all manner of changes, and I seem to have "stumbled" across this fix. I will pass my findings on to ASUS support who, tbh in their defence, have been trying to assist me for some time but alas with no success. This is working for me, hopefully you may find this works for you too.
I found the problem was being caused when the 1st guest wi-fi slot was enabled (either 5GHz or 2.4GHz). I deleted the 1st guest wi-fi and enabled the 2nd and 3rd wi-fi slots. All wi-fi connections are now stable and continue to be stable for well over a week. I tried all manner of changes, and I seem to have "stumbled" across this fix. I will pass my findings on to ASUS support who, tbh in their defence, have been trying to assist me for some time but alas with no success. This is working for me, hopefully you may find this works for you too.