power sliding door problem

On the left side sliding door when we go to shut it . It shuts all the way but pops open about a half inch after it shuts, enough to trigger the door ajar warning light. I've sprayed all the tracks, sprayed the latches to no avail. any ideas?

It sounds like the rear latch isn't working.

I'll look into that thanks.

Another thing to take note of: .... on some models, the door ajar switch is at the REAR of the door opening and has little to do with those contact switches mounted on B-pillar.