Ekko Q bug - Doesn't hit on way

This Ekko bug has been around for ages, and its insanely frustrating. I'm not sure how to replicate it or if its just random, but the bug is your Q sometimes doesn't hit champions/minions on the way out. It doesn't apply/proc your passive, and no damage or slow is applied. As far as I know, this never happens with the return portion of the Q.