I reported this issue a couple of weeks ago on my iRiver H120, and it's reproducible on the simulator (current build).
You can reproduce this bug by doing the following:
Start playback and let the song play through until just about the very end.
When there are a couple of seconds left, stop the playback and exit the simulator
Start up the simulator and resume playback.
The playback will then continue half or three quarters of the way through the next song.
This seems to be a buffering problem as fast forwarding to the end of the song won't cause this issue. I also can't get this to occur by stopping playback halfway through a song, it only seems to happen when I press stop at the end of a song.
I guess I should log this on Flyspray...