OK, I've been having this same problem as someone mentioned a month ago in the main thread. In offline mode, some songs'll just hang at 'buffering...' and never start to play.
I just grabbed a logcat, (
http://pastebin.com/J0rtYQPF -- my apologies if it's a total mess, I don't know how to restrict it to just what's relevant), but I think I can tell you exactly what the problem is just from looking at it (though maybe not the source of said problem)... here's the line (apologies for formatting typos, I'm just copying it by sight):
E/av (20126): File /storage/extSdCard/subsonic/music/Bon Iver/2009 - Blood Bank/01-01-Blood Bank.partial.mp3 does not exist
the .partial.mp3 does not exist, in this case, because it's just .mp3 (it's a pinned track). I assume a similar thing is happening with .partial/.complete with other tracks. The tracks are fine, and will play in other players.
Let me know if I can test some other cases to drill down to where the issue is.
I'm running a Samsung GNote II on Sprint, rooted with synergy rom r105. Manually changed it to store tracks on the external SD Card.
I love the app. Thanks. Also, I don't see a donate version -- Is there a place where we can throw you a few sheqels?