Nasus Q Attack Speed Debuff

I was just wondering if is supposed to slow down DRASTICALLY whenever he switches to a different target with his Q. It happened to me a few times and a few friends noticed it aswell. Whenever you Q to slam down on an Enemy Unit/Champion, and then switch to a different target during the Slam, your Q Attack Speed drops to like .3 and then takes so long to Slam down. I played for a While and I never noticed that before, so I am guessing it's a bug.