Graves auto attack will sometimes not go off properly

Recently played a ton of graves to get him up to level 5 and while i was doing that i noticed something very odd... Sometimes when you auto attack as graves, you will fail to shoot any projectiles, consume a round of ammo, and not be able to shoot until your passive allows you to reload again. Haven't tried resetting this with his e (quick-draw). So far, it hasn't been very problematic, but it seems like just a matter of time until it affects someones game very heavily, if it hasn't already. As I don't play with people who play a lot of graves and I don't frequent the boards very often, I'm not sure if many other people have noticed this. However, when i looked through bug reports most of them were calls to nerf from about 2 months ago. Sorry if I missed this elsewhere.

Note- This doesn't happen very frequently, once or twice a game at the very most. I will often play three or four games without happening at all, and considering it happens on auto attacks it seems to be a bit of a rare occurrence.