It seems that the DF protocol is sending back the bad characters. When I query the server for a list of tracks, the one you provided above is returned as "?-?
?", see below:
DF: OnCommRx(0) received: *[SendingFoundAudio][][][1][20;;2;;22][Artist;;][;;][Usher;;?-?????;;][][][][;;;;][]#
As DF are no longer in business I can't even contact them to see if there's anything I can do.