A "crack" in the system, but it's not damaged or harmful. I'm not looking for synonyms of negligence/overlooked, it's a word for the thing, conceptually, that is a result of negligence/being overlooked, like the word crack but not that exactly. All synonyms for crack don't work, either. Like, "an overlooking" or "an ignorance" but those words aren't used that way.
It's driving me nuts that this word is missing, or I'm missing it, so I'm reaching out.