Danchenko's sub-source Lyudmila (Mila) Podobedova was out for revenge
we also know that Danchenko's sub-source was Lyudmila (Mila) Podobedova (Source 5), who was journalist for Russian news organization RBC, whose information, as with Source 1, was "distant access" in SSCI terminology. She, RBC and others in suit with Rosneft.
https://www.themoscowtimes.com/2016/09/29/russias-rosneft-to-sue-rbc-newspaper-for-50m-in-libel-case-a55543