There seems to be an issue with robotics parts moving when a craft is loaded while on the ground. The effect seems to be greater the greater the gravity of the planet, but it only happens if the vehicle is loaded from a save while on the ground. Here is a picture of a robotics-mounted engine upon first spawning: Note that it is centered on the adapter piece it's attached to. Here is the same part after one quicksave and quickload:  and after a second quicksave and quickload: