I hope the above link works for you. But all you need in my opinion is any hi res flac to emulate what I have since I have this problem with all my files regardless of their origin.
If you are streaming audio via WiFi, it depends upon the capacity of your receiver what quality of files you can stream. So, your issue may not be a MusicBee issue, but the specifications/limitations of your receiver. ...I was looking into this area around a year ago, streaming flac files from MB to my Arcam Solo Neo,%u2014it transpired that the maximum the Arcam receiver could receive via stream was 16bit flac files, maximum. You may have the same issue with your player.
Also, check the UPNP plug-in found in; Edit Preferences>Plugin's>MusicBee UPNP>Configure,%u2014there you have the options to toggle between formats for streaming files upto 24bit, so check you have the maximum streaming capacity set up.
NB: I since moved to hard wire as opposed to streaming as I kept the Arcam Solo. I play Flac files up to 24bit, with no problems, via ethernet.