In the episode of the third season, "Condemned Of Space", when one of the prisoner's escapes after Dr. Smith releases him, the prisoner steals a laser gun off another frozen prisoner and fires it at the door and breaks the glass. When he runs off Dr.Smith looks around at the other frozen prisoners around him. When you see one of the frozen prisoner's holding a club, you can see the door in the background. You notice that the glass is no longer broken.