And it's easy to dismiss a mistake as "inexcusable" when you don't have to do the work yourself. Anyone who actually does work in publishing knows how common it is for mistakes to slip through even when a dozen people edit and quality-check the work a dozen times each.
There's the rather infamous Filmation pencil sketch of the Vulcan skyline, where someone has very clearly written "NO MOON". The inker never noticed.
And Harve Bennett and Nick Meyer signed off on the final sketch of USS Reliant
when it was upside down
, which is how it came to have its nacelles under
the main hull.