lynbark

This happens from time to time. Sooo frustrating. I stop the car, put it in Park. Foot is off the brake and I push the Off button. Car won't turn completely off. I get the "Ignition Still Switched On" message on the dash. I've tried turning the car on again and off... also tried driving around the block or backing out and into my garage again to turn car off. Sometimes I have to do this four or five times before the ignition goes off. If I leave it on, battery dies because car is still on accessory ACC mode.
Anybody have this problem and had it solved? Mechanics at dealer seem puzzled.