M1ner

This sounds closely related to a bug I'm experiencing. This has happened twice to me in the same manner. I was lucky to have saved after I landed one craft on the Mun, which I loaded the game from both times. Both times, went to design a craft in the VAB. Attempted launch once and vehicle loaded correctly but I reverted to VAB after realizing design flaws. Fixed things, and tried launching again. This time, loading took forever (as OP was describing) but I could hear sounds in the background as if the game was simulating something, and when the loading screen eventually went away, my new vehicle is now glitched into the first craft on the Mun. Image for reference: https://imgur.com/gallery/8K30iT8 Side note, this is one way to get a craft to the Mun