Bob,
Sounds like the problem is internal with the vocal processor. First and foremost, do a master reset of the keyboard and if you still have the problem, there's a good chance that you'll have to take it to a factory authorized repair center.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)