I've seen several discussions related to dropped internet connection in this configuration, but I haven't been able to find a suggested solution yet.

Current setup:

Hitron 2250 in router mode (IP pass-through mode still disabled) + brand new Asus AC66U B1 also in router mode.

This configuration is about 5 days old. Before this one, I had the same Hitron with Asus N56U. While having the old setup, from time to time I had to reset both devices (modem + router). Not too frequently, though. However - about a month ago I started losing internet connection. All home devices would still be connected to N56, but it couldn't get an IP from Hitron. I spoke to Shaw technicians but we didn't come up with any good solution.

Since N56 doesn't have a guest network that can be fully isolated from the rest of devices, I used this issue as an excuse to buy a brand new shiny Asus AC66U (actually, in terms of how old the model is, it's really not a brand new, shiny - but it is to me).

I configured the new router, used up all 3 guest networks Asus allows on 5GHz, used both 2.4 GHz and 5 GHz main networks, used static IPs for 3 wired connections and disabled everything I don't need (which is pretty much everything above basics - no games, no QoS, no VPN, no UPnP, more or less - nothing bur pure routing) and connected it to the Hitron which is still in the router mode. Everything works as expected except that every morning the router has no internet access. All devices are still connected to the router but without access to internet. I have to reset the router, sometimes several times, and eventually, WAN IP gets assigned (actually, it is still just a Hitron LAN address). During this time, Hitron does have access to internet. I can connect devices to Hitron LAN.

Do you have any suggestions what to try next? Pass-thought mode (need another IP from Shaw), Hitron in bridge mode or maybe another router? Or another modem brand? Maybe these two dislike each other for some reason.

Thanks a lot.