What was the key externally checkable evidence in the Ghālib b. ʿUbayd Allāh case?

Narrator Criticism, Integrity and Precision: Standards of Scholarly Appraisal

• A chain discrepancy between his oral dictation and written notes
• Both the notebook and the oral dictation identified Makḥūl identically
• He named different teachers yet his notes and dictation showed no discrepancy
• The decisive evidence was only a transmitter’s limited juristic fame