Discussed here https://farmos.discourse.group/t/adding-assets-to-a-log-2-x/1182/3
The Entity Browser in 2.x is missing some filters that were in 1.x including sorting by group and location.
While adding a birth log click Select assets under Children.
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.