Auto Attack Cancelling

Often times in game I find that when I have completed an auto attack and go to move that it will cancel, the auto could be mid air, or even have hit the target and done the animation and still not do damage. This is an issue in lane as an ADC that is becoming very very frustrating. I believe it may be latency related (71ms) average, but I was wandering if there's any enlightenment in this situation,

I'm going to try my best to describe it while using Arclight Vayne as an example:

I right click on an enemy, Vayne raises her arm, fires the bolt, and the bolt will be midair or even at the enemy character model, I go to move, and it just cancels. It can cause the blood-splat and no damage will be dealt.

Rito pls, Seth.