The errors I saw in edge developer tools were about document dom parent window not being the original. I coukd of course be looking at the wrong thing in there though. It listed a load of attributes.Any further details/reports regarding the empty Networkmap? I still ccannot reproduce the issue here, so I will need the error messages from someone's browser console to be able to investigate. The only thing I noticed was that, over https, that frame can take 2-3 seconds before it loads, but it always did. Asus did change something in that GPL where that frame gets loaded by a timed Javascript call.
I am accessing the routers over a WAN, with specific IP only allowed with Lets Encrypt cert. Its via a DDNS url as dynamic IP at the router end.