In the late eighties/early nineties I watched a film on the television. The only scene I remember clearly was when the hero is on a desert like planet. Massive great big spherical rocks were flying into a tunnel in which a machine remelted them and reformed them back into spheres. They were then fired back out of the tunnel. I don't know why.
Then the next bit I remember was that the man went down the tunnel (it was very dangerous to do so) and climbed onto the gantry and took a hammer to the controlling computer and tried to destroy it. But every piece he smashed off floated out a little way but then floated back into place. The machine was indestructible and self-repairing/healing.