It'* probably a sticky door switch that causes the delayed/inconsistent DIC reading. The DIC uses the switch that ISN't on the B-pillar... I am fairly sure it hits the bottom rear of the door.. it'* white and significantly larger than the other sensor. The lights use the bpillar sensor. Just lube it up with some 3in1 oil or something.
As far as the sticky door, everyone is hitting it on the head. The real common problem is the lock return spring rusting completely and if you open the door locked, it'll never open again until you manually unlock it inside the door [pulling door panel or slim jim]. What you have is just sticky mechanisms, you still have time before your latch fails.
'89 SSE - GX3 -190k, 155k on body - Back for another ride.