Ok, this post is from home. But the public IP might be changed at any time by the operator. I'm monitoring this thread so I can post again here when you are ready to run the fix.
Netduma is pretty much running factory defaults and after reboot works fine for hours or even days. After that I'm seeing different kinds of jams: dns stops working, dhcp does not provide ip, no external traffic at all. All these started to happen after I was forced to switch from fixed ADSL to 4G router by the operator few months ago. All the problems can be solved by restarting both Netduma and 4G router. I suspect the root cause is the 4G router but definitely Netduma isn't handling these situations properly.