Have you tried this option: "Other notes - I haven't tried yet is setting up Static IP between both routers instead of DynamicIP. Maybe there is something happening with switching the IP periodicaly...

Do you configured any VPN server ? This also can be related to an ISP cable/ADSL modem or similar.

@julamee If you have any intermediate devices before the router (modem, firewall, etc.) they should have the remote port opened as well to be able to connect. The remote management configuration on...

Try to change the 2.4GHz channel to something like: Wireless 2.4GHz ->channel:11 and Channel Width:40MHz and see if any difference.

I can see that you are doing everything you can to resolve this. And you are on the right direction. Strange thing is that this happens within exact timeframe. Could it be related to some wireless...

It could be for many reasons. As a start check your wireless settings, I edited my last post. Make similar settings for the 5GHz band (just for mode use a/n//ac or n/ac mixed). If the issue still...