There's an old saying in the writing world that the difference between truth and fiction is that fiction has to make sense. This is why research is so important in fiction writing. When I cite anachronisms, spelling errors, and other problems in a manuscript, 90% of the time, it's an error that could have been corrected with a little research.
Research is the writer's best friend. I spend a lot of time urging writers to double-check their research. Why? Because in minutes, with the magic of the Internet and my vast library of research books, I discovered a glitch in the story's timeline, the character's procedure, or a historical inaccuracy that cannot be ignored. Sometimes, what I find throws off the rest of the story, and I understand if an author's first reaction is, "I don't want to change that. It'll mean totally revising the manuscript." Yes, it's disappointing that a scene that hinges on three hundred pages is illogical or impossible. Yes, I commiserate with an author's need to protect his/her baby from deep cuts. You've already spent so much time on the story, finally feel it's perfect, and now I come along and rip it to shreds. So, of course, the author feels too protective to take a step back, consider my comments as helpful, and rise to the challenge. Since I'm a freelance editor, I don't have the power to make a writer follow my suggestions. All I can do is strongly advise. To opt against making changes is the author's prerogative, but an author shouldn't be surprised if that decision doesn't endear the book to readers.
What I discover too often are writers who write the facts around their story, rather than writing their story around the facts. Savvy readers will know the difference and will lose respect for the author who doesn't know the difference.
Last year, I wrote a post about the best habits for doing research. You can read it here. I urge you to do so and to follow these habits before committing to your story.