When we playing with my friends scp. the buttons in mainteance tunnels and plague doctor just dissapeared..

http://www.youtube.com/watch?v=ghYrRwO3 ... I7zRtU7MQg ---> the video showing the bug

in changelogs, regalis said " the buttons fixed and still occuring, ( in warhead elevator bug persist)

Happened to me once, I fixed it by exiting the game without saving. I hope it works for you! (If you saved after the buttons disappeared, I don't know if I can help you. )