First safeguard: Two names appearing in one chain do not create two independent routes. “A narrated from B” still describes a single line of transmission, even though two people are named.
Second safeguard: Having two transmitters at one stage does not establish that there were two independent narrators at an earlier stage. The full pattern must be traced from its start to its end.
Third safeguard: If a particular wording or addition is reported by only one narrator, its singularity must be evaluated distinctly from other versions of the wider report.
To classify a narration correctly, distinguish number of narrators, independence of routes, and the specific transmitted wording.