Few problems in a short story can be more jarring than an author who seems ignorant of some fact that's important to the story—or would be, anyway, if the author knew that fact. For instance, imagine a murder mystery in which the most important clue was the "fact" that the iPhone was invented by Radio Shack in 1962. Of course it wasn't, and most readers will know that, and they'll stop believing in the story's fictional world right then and there.
One of my favorite short stories will forever be marred for me by a fact that seems to have slipped past one author and at least three different editors. The story is How to Talk to a Hunter by Pam Houston. Here's the paragraph, which shows the hunter trying to apologize after cheating on the protagonist:
The problem, in case you don't know, is that chocolate is poisonous to dogs. (And this character would never deliberately harm her dog.) The next thing that should happen in this story is an emergency trip to the vet. True, a huge dog can take a small bite of chocolate and just get a little sick, but still, chocolate and dogs are never a good combination. I've never owned a dog, and even I know that.
Who doesn't seem to know that?
* Pam Houston, the author. (Although maybe, just maybe, she does because later in the story she describes the dog as "nauseous." I think that's a gross underestimate of the problem, though.)
* The editors of Quarterly West magazine, who published the story in (I believe) 1989, who should have asked Pam, "Are you sure you want the protagonist to feed a poisonous substance to her dog? That seems highly out of character."
* Shannon Ravenel, the series editor for Best American Short Stories who selected the story as a candidate for the 1990 edition of that series.
* Richard Ford, who selected Pam Houston's story out of all the candidates Ms. Ravenel had chosen, ensuring that the story would appear in the 1990 BASS edition.
* Any of the editors at W. W. Norton, who published her story in a compilation of Pam Houston's works called Cowboys Are My Weakness. Even if the BASS rules say stories must be accepted exactly as they appear in the original magazine (and I don't know if that's true), stories get re-edited all the time when they appear in later compilations.
Either back in the early 1990's no one knew chocolate and dogs don't mix, or a whole lot of people weren't paying attention to that particular line. And that's sad to me, because it's really a trivial detail in a story I think deserves its placement in the 1990 BASS. That detail could have been removed or adjusted without losing a thing.