thanks again for taking the time here @CreepyPants 
Triple checked, no CC’s on the track, new project yielded same results too. Can’t seem to figure out how to use MIDI Monitor on the Pyramid, am I missing documentation on that (sorry!)
If I have the JU-06A connected only to the Audio Output on the machine, meaning no MIDI whatsoever - and play patterns or notes from the JU-06A the machine behaves (and sounds) perfect. When I introduce the MIDI is when things go south - again though, all my other synths are behaving perfectly so I’m fairly confident it’s not a routing issue. I have “Pocket MIDI” but can’t figure that out right now either (I should go to bed, lol).
I’ve just opened a ticket with Roland since I’m well w/in warranty - so maybe this is something they’ve tripped across already and have a solution. I don’t think this could affect things, but I did add some definition files recently, and I even wrote my first one for…wait for it, the JU-06A, could that be potentially a culprit here? That post is here, FWIW. Will report back if anything progresses.