Paste a draft. See the length of every sentence, then hear it.
Nothing stands out.
How it counts: a run is three or more sentences in a row, each at least five words, within three words of each other. Runs stop at a paragraph break. A long sentence is 40 words or more. The reading compares how much sentence lengths spread against their average. These cut-offs are rules of thumb. Repetition on purpose is a legitimate choice, so treat each flag as a place to look, and decide by ear.