Without wanting to state the obvious you have checked the cables are free. Different models have different PV opperation.
They all run through a cleaning procedure that has the motor rotate fully through its opperation range. The pv changes the exhaust resonance so the engine stays "on the pipe" better. It doesent meen its always wide open. It just keeps the optimum port shape for, in the case of a race bike ultimate power. Or for the DT, torque and control.
There is a more than just a motor in the motor, er you know what i mean. Its called a stepper motor as it tells the controller its position. If this signal is confused it may well be right out of control.
Diagnosis? Could be the motor, could be the cdi or pv controller (it is separate units on some models) sticky cables, even the powervalve its self sticking. Any are possible.