In Matthew, Mark, and Luke especially, it is easy to compare stories which are double or triply narrated between them, and when we do we find those same stories have an interesting mix of being the same (even at the verbal level) and yet in other ways different (in presentation).
Early Christian churches cooperatively guarded the stories of Jesus through regular group-rehearsals (when they gathered on Sundays), and zealously worked to preserve the accuracy throughout the various tellings of their treasured stories.
• E.g. Bailey knew of this phenomenon 1st hand, living 40 years with Middle-Eastern oral communities)1
• Much more forthcoming.
Knowledgeable Jesus-bio teachers regularly taught Jesus-bio to others with some measure of formality (as rabbis did to students).
• “Teachers” oft checked/relayed Jesus-bio.
• Didache 11, 13: “teachers teach what you already know”.
• E.g. Apostles oft started, taught, & visited churches.
• “Delivered” & “received” indicated teachings from a teacher • Papias: “Jesus-witnesses xyz are still pop-teachers (in AD 80)”.
• Christians felt Jesus-bio teachers deserve honor.
• Christians used/employed only qualified tradents.
• Christians strove to match reliable tradents on Jesus-bio.
• Jesus constructed memorable teachings.
• Lk says “the witnesses were the teachers”.
• Apostles weren’t trained in memorizing.
• The Gospels are full of minor differences.