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I have found some pretty cool contemporary jazz midi files on the web.



This is your problem. Never say never but this is usually nothing to do with your synth. It's simply responding to commands embedded in the midi file.
Way too many potential things to list here except to say you're dealing with a file that somebody else created and who knows what he used to create it. Trust me, they're not all created equal. Maybe that person was a total idiot, maybe the file started out great and this person found it and modified it to fit his synth or added extra parts to it, it could have sysex in it, it could have tons of controllers in it, lots of things to think about. Hung notes tend to be pitch bends with no stop command after them, usually stringed instruments.
After 6 or 7 years of downloading files I have a folder with about a dozen files in it that I still can't get to play right and I'm fairly good at midi now. If you really want to learn midi then this file could be a good teaching exercise for you, if you just want that song then Google another version of it, you may find one that plays correctly.

Bob

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