Check your Vis motors, they are supplied with power for around 5 mins after ign off. If the Vis motor has a failed final drive inside then the motor inside the unit will run untill the ECU cuts the power.
Simple to check if it is them just unplug them and see if the noise stops. If it does leave disconnected until you replace them.
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Dave...
Lost a few stones  and a Gall Bladder and part of a bile duct and all of my dignity in the suppository incident
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