Can’t have your VPs son getting caught up in Ukrainian corruption. Can’t have a scandal free presidency with that out in the open. Had to be squashed and it was Biden’s mess.
December 29th 2016.
https://www.nytimes.com/interactive/2017/02/14/us/politics/flynn-call-russia-timeline.html
The call on the 29th is where the FBI went after Flynn with regard to possible misstatements.
Rice’s email to herself indicates Comey had concerns over the volume of call Flynn and Kislyak we’re having. Which could mean they had many conversation prior to the 29th. Or they could be lying.