I ran into the same issue we had at Bob’s with a car showing a drop-off, but that car was never on a pick-up order.
Looking at the train details, the “missing” car is properly in the make up of the train. In my case, was a yard pick-up at the origination point. The bug is in the reporting of the train orders. The “missing” car is not in the group to be picked up at the yard.
My work-around was to go back into the train detail and un-check that car before terminating the train because I didn’t notice the car missing until I was a long way away from the origination yard.