It Conquered the World (1956)

Revealing mistake: The alien is starting to mess with all sorts of mechanical and electronic devices. One of the first ill-effects shown is a large industrial cable reel that is dangling in midair when the mechanical arm lifting it is paralyzed. Problem is, you can see the operator has his hand on the controls and is stopping the crane himself using the lever, nothing alien about that. (00:14:50)

Sammo ★

Paul Nelson: It must be some kind of cave bat.