Andreas Hartl wrote to suggest unit confusion as a blunder.
In the movie Screamers (totally B-movie quality) the hero travels to the origin of some highly sophisticated weapons system: it’s a mine where those weapons were used to defend it. The character traveling along with the hero explains that this mine was the source of the valuable mineral Bernylium. Bernylium was mined “cubic-ton by cubic-ton”. I do not recall mass having three dimensions… (This is from the german translation, I cannot guarantee that the original script contained this inaccuracy)
Or how about confusing light-years and parsecs with units of time. In the Babylon 5 episode “Messages from Earth”, Lenier said the pressure outside the hull of the White Star was reaching 200 gravities. Gravities? Since when did that become a standard for pressure?
(In retrospect, I think the writer of the episode was confused with specific gravity which still was the wrong unit for pressure.)