This may or may not be a bug, and I don't know if it's in KP2 or Sonar, but twice, while using the above mentioned software this evening, an instrument all of the sudden went a quarter tone (50 cents) flat (under pitch). Both times it was completely random (happened on its own) and both times it was exactly 50 cents under. This occured when I had the player loaded with 15 instruments, but the piece was not playing when the event took place. Shutting down all the software and starting it back up again cured the problem, but it's still strange that it happened in the first place, much less twice. The piece did not involve any pitch bends, so it didn't just get stuck because it didn't reset to original pitch.
I haven't been a very frequent used of JABB/KP1 (my work didn't call for it) so I don't know if this issue was present in KP1 or not. Maybe this will be familiar to you? If it isn't, I'll keep plugging away, and if it happenes again, I'll try to write down the exact circumstances, if there are any.