Hi,
I am jf, the developer for upmpdcli. This issue has little chance to be specific to runeaudio. Could you please get in touch with me: jf at dockes .org, I would like to try and fix this, but I'll need to know what control point you are testing with. If I can't install it here, debugging may be a bit complicated, but hopefully, we will be able to see what is happening by looking at the log.
As far as I know, metadata display works fine, or mostly fine, with Bubble, Kinsky, Kazoo, JRiver, Lumin and my own upplay, but there are so many CPs out there that I've obviously not tested them all, and I guess that there may be circumstances where those I did test will have problems.
Alternatively to email, you could file a bug on GitHub:
https://github.com/medoc92/upmpdcli/issuesCheers,
jf