Sure. Re-started the server (incl. rebooting the Pi).
p.s. the new server actually seems to (also) have something running at port 80 (The previous server did not have). Unfortunately I can’t change that one to another port. Can this be related?
I’ve had lots of trouble trying to proxy to unifi controllers. The unifi controller changes the HTTP location which can tend to break proxies if whatever it tries to redirect to isn’t proxied also.
However, instead of trying to fix it I’d recommend looking into the Ubiquiti Beta Network Monitoring System:
You can run it on a $5 digitalocean VPS or whatever network assets you have available. It’s nice because it also works on the Ubiquiti edgemax routers/etc as well as a unifi.
Otherwise what I would do would be just to run SSHD on the raspberry pi and then use a SSH tunnel to access the unifi controller, it’s more of a pain in the ass but it will work consistently.
Actually now using this solution (Unify CloudKey with cloud access enabled). Accessing it via cloud access not needing any proxy. So I have a solution allowing me safe access from remote location now. However still surprised my ‘old’ solution via Caddy does not work anymore.