[Bug?] Lucian Passive 'Lightslinger' not always proccing?

I'm not sure if I'm the only one who's noticed this recently, but I feel like since his tweaks I will sometimes not get the passive to proc. The buff uses itself up but the second shot doesn't fire and my E cooldown doesn't get reduced.

I'm having a hard time reproducing it consistently but I notice it at least a couple of times in most games I play...

Now that the E cooldown is linked to Lightslinger, its pretty noticeable when it missfires, since I'm expecting to be able to use my E and it doesn't come off cooldown. Makes stringing his abilities together fail completely when it happens and its very frustrating.

For clarification. The first shot fires and hits the target, but the second shot from the passive will fail and not fire. The Lightslinger buff still gets used up.

I'll try and see if I can reproduce it somehow.