Both of my DMC12s had the same basic problem, when inserting the key there was resistance, had to turn the key over a time or two, sometimes wiggle it a little to get it to work. My basic remedy for key cylinders is WD-40, an excellent penetrant and lubricant. Powdered graphite has never worked for me, it's also a conductor (I'm not going to say it can migrate and take out your O2 sensor but it is worthless in lock cylinder applications) on my latest one I also applied a film of silicone grease (that I mentioned a few posts back) on the key, worked it in and out a few times and it's like new. Les