Is the magnet in between centered?
I've read that if your car takes a fall, it can knock that magnet loose to one side. Re-centering the magnet and glueing it back to it's plastic encasement can fix this problem.
Just a thought, otherwise I too, am stumped!
This photo shows the magnet (silver colored) in it's proper location.
http://www.ausmicro.com/technical/bi...o/DSCN2433.jpg
Let us know how you make out. Good luck!
Jon