Hey I have also noticed this, I just bought her about a month ago and have been playing her in about 75% of my classic 5v5's (which isnt much) but I noticed sometimes her AA's would not do damage, the q didnt noticably increase in damage until after I bought bloodthirster, even with leveling the ability, it did the same damage (seen on damage icons above targets heads) until I bought bloodthirster, then the level scaling and bonus AD from items applied and I was doing normal damage again. This may not be exactly what happened because bugs can be hard to understand, but this is what I noticed, some auto attacks just would not connect although the projectile exited her weapon and my AA animation played out fully. It has only happened in a few games though. Not sure of all the steps to reproduce this issue but I will post here again if I can figure it out.