My 2013 LaCrosse does not trust me. Occasionally, it won't respond to the key fob. If I open the door using the key, the car goes into lockdown mode. Not only will it NOT start, it confiscates the key and won't allow it to be removed! The only work around is to disconnect the battery and tap the battery post with the cable until it comes back to life. I bought the car for my wife and she now refuses to drive it having been stranded in some dark, rainy places. The car battery tests good and I've replaced the battery in the key fob twice. Anyone have any suggestions?

Welcome to the forums!
Sounds like you got a few issues going on there.
Cars can do some very weird stuff if the battery/charging is weak or has poor connections.
Was the battery load tested? Make sure those terminals are clean/tight!
Are the recalls looked after? http://www.cars.com/recalls/buick/lacrosse/2013/
Key stuck in ignition...hmmm time to talk to the dealer...is it still under warranty?

You have 4yrs/50K miles, bumper to bumper coverage.....so if you have under 50K miles, and the vehicle was put into service after Feb 3, 2012(today would be your last day if put into service on Feb 3), then you still have full coverage on your vehicle....

Thanks for the replies. I have clean battery posts/cables, but cleaned them anyway. I obtained a new key fob from the Buick dealer ($100+). My wife drove the car for a week with the new key and was stranded again at the grocery store today, with groceries piled up outside the car when I arrive to rescue her. The car eventually came back to life when I did the battery post cable trick mentioned earlier. She also reports that the backup camera screen occasionally goes all blue with no image while backing. The radio also goes off sometimes for no reason, and the infotainment screen goes blank, but eventually comes back to life while driving. Bummer. The car has 53K, so just out of warranty. Buick dealer finds no bad codes, but I suppose they get erased when the battery is disconnected. At wits end. Don't know what to do.