Felt like I should report back on this as it has now been 3 weeks & everything has been resolved.
Contacted DSI customer service. Some of the best customer service I have ever dealt with, btw. As part of the process, I had to record my issue via video and send it to one of the reps, which makes sense, this is standard. The rep suggested it might have something to do with the PCB so DSI sent me a new PCB in the mail (after a $200 deposit). I replaced the PCB and documented the process with pictures--problem still persisted. I recorded a second video and sent it to DSI customer service. Customer service rep suggested it might be an issue with the keybed & that they have never seen this before. A new keybed was sent to my address, which I received this week. Spent some time yesterday replacing the entire keybed (a somewhat laborious and lengthy process) and today, finally, I can play my Prophet '08 sans problèmes!
Perhaps this information might be of help to somebody else in the future, provided they have the same or a similar problem, though, oddly enough, as I mentioned before, it seems I am the first to have had this type of issue with the Prophet '08.
Anyway, thumbs up, it's done now!