Sounds a lot more like an issue with the SansDisk mp3 player's ability to crossfade between tracks, or support gapless playback, both of which can change between different players...
I'd suggest another look at the MP3 player's manual, with special attention payed to any section to do with track playback.
Only other thing comes to mind is whether the skipping tracks are on the expansion card or not. If so, perhaps you have a compatibility issue (even though they are both SansDisk products) with the card. Is it an HD card?
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