Delay on targeting camps/minions with autos

Sometimes when I'm farming it takes more than one right click to target a camp/minion. I'll be moving and then when I click on the target, my champion will just stand still. I'm clicking directly on the minion, and it has the red border around it.

My ping almost always hovers around 60-70, and I never drop below 60 fps. Is this a bug or a setting or am I just doing something wrong.

I know I could probably just solve this by enabling attack move but I've always played without it and it would take a while to get used to.