Glad your first trip was a good experience!!
We had a similar bathroom door problem, though it never came off the track. Our pin did not connect with the ceiling stop and the door was constantly swinging open as we traveled. We tried blocking it with a rolled up rug, until I forgot the rug was there and took a flying fall!!
Do you realize the spring pin is adjustable? After adjusting the pin, ours still wouldn't secure the door. After pursuing the issue further with Thor, they made us 2 spacers that matched the original stop. We drilled holes through them, and once installed the problem was fixed!!!!