I ran into a similar issue trying to reverse proxy to mine at unraid.myweirdoname.duckdns.org with DNS challenging and NGINX issuing a cert. Seems that part of the GUI trusted the cert chain, but not others. It manifested in docker update windows going blank, no listing of drives, and popups like Logs and Terminal window closing themselves. As soon as I accessed via IP or by the blahblah.myunraid.net it worked fine.
The issue isn't bothersome enough to troubleshoot yet, but I'll update if I get there.