Hi Aidan,
Below is a post from a while back pre-Classics, but something I found with 5th generation iPod that might be the same issue. Read it, try it and see if you think it is the same thing...
This appears to be a bug in iTunes I think. I have noticed that songs that do this on the iPod always do it. In other words, if you replay it, the hard stop is really there.
What I also found is after I sync back to my iTunes, I go to recently played and look for that song. Note the time and it will likely be the truncated time. Now double click the song and you probably will see the time change back to the correct time as the song begins. Now right click the song and change something about it, like reset the play count or give it a star. Anything that will force it to reupdate back to the iPod.
I find after I do that, the song then plays fine on my iPod.
Because of this bug, I use a 3-star rating to flag truncated songs. In iTunes I have a smart playlist that is all 3-star songs (I normally don't use the star rating except as flags for various issues). So when I am listening to my iPod and I find a truncated song, I go back to the song again (since you have now jumped to the next song) and while it is playing, I click the middle button to go from volume to playback position and again to the star rating screen and I assign it 3-stars. nd now I can skip to the next song and forget about it.
Next time I plug it into my iPod, any 3-star (aka Truncated) songs go to my playlist so I can quickly find which ones had the issue. Double click them to reset the time in iTunes, then reset the stars to zero to remove them from the playlist and force them to be updated back to the iPod. Done!
Patrick