Unity Animation Keys Problem

I'm having trouble creating an idle animation for a weapon. The animation is being made for the Mace, I have key frames at 0,2min and 4min. Whenever I try to move the key frames at 2min (particularly a slight left rotation on the y-axis), all the other keys dip down dramatically ruining the animation. When I then play the animation the weapon goes on to rotate wildly in front of my character.

Any help? Thanks in advance!

Parents/Children: Main Camera -Melee --Mace ---Grip