So I was playing Space Engineers with a friend of mine. We have a mod that added atmosphere and reentry. When you start to re-enter the atmosphere (the ship is damaged and destroyed) the game crashes, but if there are no players on the server, the game does not crash. It crashes on the host side. The mod's developer said it was a bug in the game, so I submitted it to Keen Software House. I will put this crash log here if anyone tells me what had gone wrong.