Well this happened to me in cheat mode while i was checking how many LABs you can fit in a T3 transport. It is the very first thing i do, so it is after a few seconds of game time.
Maybe cheats have something to do with it and it's probably nothing but i post the replay here in case there is a bug that need to be investigated someday.
As you can see it happen with multiple loading commands. The transport seems to think he is empty and allows multiple labs stockpiling in the same spots i think ?
The first load command loaded 27 LABs instead of 28 and the two other one loaded 28 in two batches.