User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20161022104148/@comment-9595671-20161024005550

Loki did curse Issei actually, it just wasn't related to Raynare, and the two curses enhanced each other due to how Rossweisse defined it was the kind of curse that ate at one's doubts. This is how he made the fake Juggernaut Drive that Issei fought.

Ironically we didn't know of this curse (which admittedly is more like a subconscious defense in Issei) until Volume 10, the instance we saw of Raynare's curse during Season 3 was an anime addition, and admittedly one that worked since it does help connect to why he's afraid of getting close to the girls.