Hecarim E (Devastating Charge) [GAMEPLAY]

I recently picked up Hecarim with the preseason, and I've found that a lot of the times while E is active he will randomly attack people, and it can be incredibly annoying for various reasons: 1) You're trying to run away so you activate e for the movespeed, and then hecarim turns and uses the E-modified attack on somebody chasing you; 2) You're trying to focus down x target on the enemy team but instead you randomly attack y target.

I've noticed it in games over the past week or two but kinda dismissed it as just a misplay for the most part until today when it was VERY apparent that there was no way I misclicked or anything like that.

In the video I uploaded it can be clearly seen that I'm trying to run towards my base gate, and have no idea how or why my champion decided trying to fight shaco was a good idea.