Sounds like you need to get a VDR from the stealership (vehicle data recorder). Pretty much you drive around with it plugged into the OBD port and when you experience this problem, you hit the red button and the VDR starts recording every aspect of the vehicle; PCM inputs/outputs, BCM (Body Control Module), ABS, etc.

Techs can't fix something they can't see, and in this day and age while module can fail, they usually don't and people foot the bill with these expensive unneeded repairs.