RT-BE96U (Merlin) + Xfinity TG4482A (Bridge) - Periodic Internet Loss (every 3-4 weeks)

[random9]

I have an issue where, about every 3 to 4 weeks, my Internet connectivity stops working. The Asus router says No Internet Connection. This never occurred with my older RT-AC68U with Merlin firmware that I had used for years and only started about 3-4 weeks after replacing it with new Asus hardware.

The setup:

• Comcast Xfinity TG4482A modem configured in Bridge Mode
• Asus RT-BE96U with Merlin 3006.102.5 – configured Wan -> “DHCP query frequency” : Aggressive Mode.

Note: this problem did occur with prior Merlin firmware on this device – e.g., the problem is not specific to just the latest version. Just never occurred when I used the RT-AC68U.

I’m at a loss to troubleshoot this. When the problem occurs:

• Local connectivity on the network still works, but there is no means to access the modem, even by IP. The route to the 10.x network between the router and the bridged modem (to access the modem's web interface) is inaccessible.
• Power cycling the RT-BE96U is not enough. That does not resolve the issue.
• Power cycling the TG4482A modem is not enough. That does not resolve the issue.
• I have found that if I turn off both devices. Then, if I power on the modem, let it boot, and after, power on the router, everything comes up and starts working again.
• I did try a different ethernet cable, just in case, but it did not help.

For now, I have just changed the “DHCP query frequency” to Continuous Mode in hopes that it could help. In the meantime, are there any other suggestions?

Any ideas on what might be going wrong here? What can I capture in the future to better troubleshoot this?
Seems crazy that it all worked for years with the AC68U, but not the BE96U.