The JP-8000/JP-8080 (almost identical) has got quite strange MIDI-implementations. To use it successfully in a sequencing setup, there are certain considerations to take.
Here you have two examples of users trying to cope with the JP:
I have used some time investigating the JP myself, and created a “compendium” for personal use, with examples and sceenshots from Cubase. As I said, It is created for personal use - it is not very neatly designed and the writing is fragmentary - but I guess it could help you to get out of certain problems regarding sequencing with the JP…