Gameplay Rengar Empowered E bug.

[GAMEPLAY] I have been having a rengar bug the past few games when my empowered e goes on cooldown but i can use w and q.

How to make this bug happen:

1. Go in a bush and as soon as you right click the target to jump, press w,
2. E them when you land and hit 5 ferocity stacks (assuming you already have 4)
3. You should see a cooldown on his E but not on W or Q as they have been reset because their empowered. If this matters, I did it on a maokai.