You know, I see bloopers like the one you're describing on television as well. Often, I read things in books that suggest the writer hasn't researched his topic enough. However, in their defense, I expect that producing a show like that involves seeing to a thousand little details. It just stands to reason that they're going to miss something once in awhile and usually it doesn't interfere with the entertainment value of the show. These days, I would assume that 99 percent of their viewers wouldn't recognize whether a sewing machine was positioned backwards if it were sitting right in front of them.