«وَسَبَبُهَا أَمْرَانِ»
There are two causes of such uncertainty.
First, a single transmitter may be described by several names, teknonyms, epithets, or affiliations. Unless these labels are recognized as belonging to one person, a researcher may treat a less familiar label as an unknown or different transmitter.
Second, a transmitter may have very little transmitted material, with few students reporting from that person. Biographical information may consequently be scarce. This leads to the discussion of al-wuḥdān; where a narrator is not named at all, the case is al-mubham.
The remedies differ. Matching multiple designations may resolve the first problem, while the second may require independent biographical information and critical evaluation.