I just had exactly THIS issue and found that the switches, which are located in the latch assembly on the rear door, commonly get gunked up, and there is a little ball or something that gets where it won't fully register with the computer. Anyway, just jose them down with WD40, and there's about a 75% chance you'll have no more issues, for about a year. The side doors have contact plates that can be cleaned too, but it's usually the rear.
Ben | 
