Right, Frank, it de-dupes on shuffle, as described here in the FAQ. What you're seeing there is normal behavior.

Edit: re-reading Frank's post I think that he might be seeing the same thing that GooseGog is seeing. Even with shuffle off, his full-player-playlist doesn't show as many tracks as Emplode says he has.

The problem GooseGog is complaining about seems to be a different one. At least in our private e-mail exchange, he seemed convinced that it was something different than what's covered in that FAQ entry.

I have a question for Frank and GooseGog:

Are any of your playlists tagged with the "Ignore as Child" flag? That might produce the behavior you're describing.