I’m not sure exactly what you are saying is happening here.
Are you saying that when you first connect, a particular song shows a correct song length, but as soon as you play it through iTunes, the song length changes to something less? Like 10 seconds?
If so, that’s a “bad tag” problem. iTunes is reading the tag (since it can’t read the tag until it starts streaming the song) and the header must be wrong, causing it to decided that the song is only 10 seconds long.
You might try removing the id3 tag from that song and retagging it, then seeing what it does.