This happens to me as well on PC, only it occurs EVEN IF I save and then exit to the Title Screen. Oddly enough, it has not happened every time, nor has it occurred with any other vehicles. The first time I had it happen was after I built the cyclop…
2020, and still having the same problem. However, It could be because my save is a couple of years old. I will start a new game and see if that changes things, but in any case I'm disappointed all my old progress was for nothing.