This appears to be the fix - moving from the ASUSCOMM.COM DNS provider to a DDNS.NET address has given me stability. I am still monitoring the old asuscomm.com DNS, and this URL (to the web interface) has been reporting up and down multiple times over the last few hours while the other DNS continues to report 100% uptime.
Solution - Avoid the Asus provided asuscomm.com Dynamic DNS service, it doesn’t appear to be a service they consider critical to their solution stack. Follow the docs and use a more traditional dynamic DNS provider. In may case I was able to use noip.com and a docker to keep me in a pattern I am comfortable in.