This isn't a solution, but may lead me to follow this thread:

Does it work with some assistance? That's exactly how mine behave. They stopped working, but if you help it along it does move with the motor...it just needs a little help. Maybe the motor has become tired. Signs of it about to go out.

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"Patty" - 1994 E320 Touring "Sportline" 172/174 124.092
"Lucy" - 2006 Toyota Land Cruiser