That is an odd one.
Everything seems to work on Mosaic except for this issue, yes? One thing I am not clear about. Is Horse With No Name a local file served from your NAS or is it via another streaming service?
I think we can forget about discovery issues with your network. You also seem to have taken all of the “first responder” remedial actions. What does not seem to have been considered is your NAS server if it is a local file. Try rebooting this. What server software are you using?