two theories:
1. you could be having a bad door sensor-yes really. try to cheat it or swap with another. they CAN go kinda bad, slowly. let enough voltage to show closed, but not enough to complete the safety circuit.
2. i had it once where it was a weak registration sensor. make sure the glass is clean first, inside and out. of course.
then go into diagnostics, logged in as svc. go through and check your sensors. you can flip them on and off and get the reading. when mine was going bad, this ALSO served to reset the "jam in area 2"
good luck