I'm running Unleashed on a couple of R710s version 126.96.36.199.203 (latest) I have set up a guest network and utilizes the built in Captive Portal hosted on the Master AP. This works well until I add a custom certificate under Admin&Services -> Administration -> Certificate -> Import Signed Certificate.
I'm importing a CloudFlare Origin Cert (with my internal domain i.e *.myintenaldomain.com). This also works well using the Unleashed UI the cert is present and working as expected.
Now when I test the captive portal, on Linux, connecting to the Guest network, Clicking sign in I get "If you are not redirected within 3 seconds, please click here." And the link is pointing to: http://cloudflare/.