KN7000 getting loud extraneous key played on chord changes. Does not happen every time but during a song it could happen 4 or 5 times. Can't make it happen it just pops up. Its like someone just hitting 1 low key while a chord is being changed from one chord to another.

Anyone had this issue or any ideas?

Are you playing live or does this happen in a sequenced song?

It happens when playing live

In 'part select' have you got 'left' switched on - because that could create that sound dependant upon the instrument selected for 'left'?

Yes, with the accomp on, it could be part 16, the chord bass, which sounds when you change key.