Salam alaykum wa rahmatullah
Just two quotes that seems interesting to me.
Ali ibn Madini relates: Sufyan ibn Uyaynah was told: «Zararah ibn Ayun narrates a book from Abu Jafar». Sufyan said: He didn’t ever see Abu Jafar, but he used to gather his ahadeeth».
( Salahudeen Ali Abd al-Mawjood «Sufyan ibn Uyyanah» p 134. Maktabah Darussalam).
Same opinion was reported from Sufyan Sawre. Zurarah didn’t see Abu Jafar. (Mizanul itidal 2/69/#2853)