Look at the fight scene between Dark Helmet and Lone Star. If you watch the part right before the rings get twisted you will see the special effects were a little off, because one of the beams is about 2 inches off the ring. You might need to pause the movie to catch this.
Listen! Spaceballs was supposed to be obviously fake! it was a comical version of Star Wars! Why would they want it to be perfect? That would take away the whole comical purpose. (Though I do think you must have a very quick eye in order to have caught this slipup.)