Yoric E Bug

Yoric Mori's Omen of Famine seems to have an unusual interaction with Tristana's Rocket Jump. In a recent ARAM, every time I cast Omen of Famine on Tristana while she was performing a Rocket Jump I would go through the cast animation, the damage would be dealt, I would be healed, but no wraith would spawn and the ability would not go on cool-down. Could someone please investigate further?