I can no longer edit Apache's config files of Virtualmin servers via the Virtualmin panel.
Go to: Virtualmin > select a domain > Services > Configure Website
Clicking "Edit Directives" pops up an error message:
Missing file to read at apache::/usr/share/webmin/apache/manual_form.cgi line 86
This has been happening ever since I changed all VirtualHosts to 127.0.0.1:8080 to use nginx as reverse proxy (serve static files w/ nginx to handle most of the load, leave the rest to Apache2). Everything works perfectly, except I can no longer view or edit the directives via the UI.
Newly added virtual servers seem to work fine.
Another issue is that the "Change IP address" functionality doesn't seem to be built to allow an IP address to be used for the VirtualHost and another IP address for the DNS configuration (e.g.: 127.0.0.1 for VHost, and another external IP for DNS).
This last issue can be ignored because I can live with it, but the first is becoming a real problem.