I was using debug mode to test out some logic gate stuff, decided to take a break so I saved and exited. When I loaded it again later, moments after unpausing the game, it crashed. If I use debug mode to destroy or deconstruct the first door on the left before unpausing (highlighted in the screen cap), this prevents the game from crashing. I re-added the door and soon enough the game client crashed again, the next time it was activated by the logic gates.
Load the saved game. Unpause. To prevent the crash, delete the door on the far left before unpausing.