Hello Anthony,
Have you thought that perhaps the original sequenced files were for an older instrument?
Some of the older patterns and styles will not work on later models - because of programming variations.
Also, perhaps the current sequenced styles have been 'tweaked' on, or converted, from another instrument which could also cause problems.
I think I would try to download & save the sequenced files to a floppy or SD Card (whichever the PR804 uses) and see whether they play o.k.in the instrument. If they do, save them to your PR804, then download to your laptop either direct from the instrument, or from the originally saved floppy/SD Card.
Hope this helps.
Audrey