I've got the exact dame problem! It's not to do with black spots or battery or re programming or Doors left open! I am trying to find out also what is causing it and it's a pain! The light flashes to unlock car on remote but doesn't when I press lock! It's the same on all my brand new keys I've spent 100s on remotes still the problem is there! I have found that yoy can lock mine but only by pressing the unlock button 1st then very quickly pressing the lock button, that works even tho the car is already unlocked it wants me to press unlock then within 2 secs press lock and bang... The light fla