1996 Mercury Villager latches & locks problems

I had a low impact accident where the front of my vehicle hit the back of another vehicle. (forgot to put car in park and was about 4 feet from back of another car on slight grade, well you know the rest). After the accident the sliding door began to "pop" enough for the ajar door light to come on but not enough for the door to actually open. I have checked with the people that gave estimates on repairs and was informed by every one that it was not a result of the accident.

While I am driving the sliding door will pop. Currently it does not completely open, but is does become unsecured. The interior lights come on and when driving at night inhibits my vision and makes driving unsafe. My children are also the passengers near the door at this time and I am afraid that the door will fly open and cause harm even though they are in safety belts. I have had a mechanic look at the latch and he sees nothing that should be causing this to malfunction.