Revealing mistake: At the point where someone gets a small bruise on the upper arm, the crew are all in a pile and thrashing about on the floor. There are 5 pairs of legs instead of 4. Arthur is in his pajamas, Zaphod is in orange trousers, Trillion is lying on top of Ford and Ford is too far away for them to be his legs. [The fifth pair of legs belong to the person playing zaphod's third arm - doesn't mean it's not a mistake, but that's where they come from.]
Revealing mistake: At the paramilitary base, after Bill tells Bunker he has "a real cute bivouac goin'," it cuts to a shot of Ralph searching for Bill's location, and the stunt apparatus is visible at Ralph's waist area. (00:21:30)