I found out the problem is
I found out the problem is not only with 2015 Ram 1500’s ........ I have a 2016 Ram 2500 that has been doing the same thing for the last 5 months ...... one day I was “LOCKING” my truck with the Key fob and the tail gate “FELL OPEN”
...... I play with the fob lhitting the “LOCK BUTTON” several more times and the tailgate opened again and again ........ the tailgate is not opening because of going down the road - it’s opening as the key fob is locking your truck - when you leave where you stopped at gravity or the first bump in the road take over and the tailgate falls open - contact Chrysler customer service and tell them to look up my repair case at Preston Dodge, New Castle, Pa (repair to be done on / Red 2500 heavy duty 4x4 on Tuesday November 14, 2017) I only solved the mystery my luck as I was walking behind the vehicle when I push the lock button and it happened - Good Luck all - Dave