Wild Mass Guessing regarding Harley Quinn.
The solo series is a fantasy in Harley's head
Because of DC Comics' current philosophy of emphasizing canon over continuity, the way Harley is portrayed in her solo book, and the why she's portrayed in Suicide Squad are not compatible. But it still could work. My guess: Harley's solo series is actually not happening, but is just a psychotic episode in her head. Suicide Squad Harley is the "real" Harley in the DC Universe. The Harleys in her solo series and Suicide Squad really are two different people
The Nu-52 controversially retconned in the idea that the Joker constantly warps women into new "Harley Quinns" and kills them when he gets fed up with them. This makes it entirely possible that the kooky Harley from her solo series and the Ax-Crazy one from Suicide Squad are two different ones who both broke away from him and survived. Harley got shot in the head.
Much like her counterpart on Gotham, Harley was shot in the head at some point, and the bullet in her brain is affecting her. Hence, the differing portrayals of her in her solo and in Suicide Squad.