«نَحْوَ حَدِيثِ الْمَسْتُورِ إِذَا تَعَدَّدَتْ طُرُقُهُ»
For example, a report transmitted by a mastur narrator, when its relevant chains are sufficiently numerous.
The outward condition of a mastur transmitter may be known while his complete inward reliability and precision have not been adequately established. The report's assessment can differ when considered alone and when credible independent supporting routes are brought together. One must still check whether those routes repeat the same error or depend on a common weak source.
Central point: evidence can help compensate for a relatively mild uncertainty, whereas established fabrication or an extreme failure of retention is not erased simply by increasing the number of cited chains.