I tried cleaning the case and the ignition switch, and also tried rotating the key 180 degrees, but the car still does tricks with that key. I guess I have to cough up another $200 if I want another backup key, or perhaps if I take it apart I will notice something fixable (not likely).

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1996 C280 289K Traded
1997 E420 167K Traded
2001 S430 240K Traded
2010 E550 4matic 80K
2000 GMC Jimmy 198K Gone to Boneyard
2003 Camry LE 196K
2011 Mazda3 i Sport 31K