Playing on a zero population server, I climbed to the roof of the Elektro powerstation firehouse. As I was trying to pick up ammo from the roof and place it into a gun, the drop down menu stuck on "Receiving..." I closed out of the inventory screen and re-attempted two more times. After the third try, when I closed out of my inventory, I rapidly got two messages pertaining to "Your leg is broken" and the death screen. Hitting the "escape" key gave me a view of the bottom of the firehouse, indicating my body had fallen through the entire tower to the bottom.