[GAMEPLAY] Runaan's causing Kalista E to double cast

Been playing some Kalista top, rushing Runaan's. As soon as I build Runaans, I start noticing a bug with Rend (E). I'll get some stacks of my passive onto minions, and then hit E to execute them. But sometimes E double casts, executing the minions but then immediately casting again and putting the ability on cooldown. You can hear it casting twice.

I'm fairly certain this is happening when there are projectiles still in the air from the Runaan's orb that are applying right as I'm casting Rend - so it executes the stacks that were there but then sees that there are new stacks and casts again. But since those new stacks aren't enough to execute the minions, the ability goes on cooldown.

TL;DR: Runaan's seems to be causing Kalista E to frequently double cast. I can attach a video later today if needed.

Reproduction (as far as I have been able to determine): 1 - As Kalista, build a Runaan's hurricane. 2 - Apply stacks to minions. 3 - Cast Rend mid attack animation. 4 - Rend should double cast if the conditions described in my post above are met.