Thanks for the information. I had this similar problem (version 9.13.0.0.232) as I did installed a wildcard certificate in order to users not getting any untrusted certificate the Guest Access captive portal. However, users in this guest access network are being redirected to the Zone Director's IP address and not its FQDN (note: I have an internal DNS server which resolves this).
Btw, in the latest version (9.13.2.0.33), this might not be needed as they reverted back the default Guest Access Captive Portal to HTTP. But if you still wants HTTPS, this can be activated with commands mentioned in the release notes.