I would guess the playfield was raised with the ball still in the machine. I just got a project machine myself that was missing key (and since it was a completely unexpected find...I didn't have my tools to drill lock). Luckily the back box was unlocked and I could remove bolts to fold down head. But, I was scared to death that when we turned the machine on its back for transport up the stairs that this is exactly what would happen. I got lucky, but can see this easily happening.

Take out the ball...the buildings are very thin and a loose ball can easily fly through one when moving the game.

Been a long time since I moved mine, but...If set up correctly, you will need to use the keys to remove the backbox glass and open the light panel behind. There will be (4) 1/2 inch bolts that hold the body and head together securely. Remove these bolts, close light panel, re-install glass and lock down...then there is a hasp (I believe) on the back box that you can release to fold the head down. Carefully lower head, might want to place something between head and body.