I have been paying attention to historical errors in fiction lately. When I read an historical I am always on the lookout for errors. Once I find one I settle back to enjoy the rest of the book. I think there are four basic reasons for them:
Not enough research: the author didn’t dig deeper than the reader.
Too much research: here is this nifty new thing e.g. zippers which were not in popular use until a long time after they were invented.
New research: when I wrote it, it agreed with the available scholarship. Since I wrote it this something new has been discovered.
Perception: the author sees things through the eyes of a modern person. The stagecoach stuck in the snow spinning its wheels to get out, or the woman who refuses to wear a cap in the house because she sees it as an example of the oppression of women, rather than a practical article of clothing.
Over the next four weeks I will take each of these apart. I am struggling with them all now as I start work on my new novel.