Why does my animation warp when I adjust the scale in Unity?

Hi, recently I got an animation working form 3Ds Max 2013 to Unity3D, it's a door. Originally when I rescaled the animation in Unity the scale of the object was fine, but the scale reset to one when the animation was playing. I fixed this by using the 'reset XForm' modifier in 3DsMax and redoing the animation via a single bone. However after this, I noticed the door was too thick, so I halved the scale of the 'Z' axis in the inspector.

This worked when rescaling the object, however again when the animation playes and the door opens, the model warps along the 'z' axis. I have made it a child of an empty gameObject and it still doesn't work.

Does any one know why this is happening, have I done something stupid? I've trawled through the web and looked at the scale setting.

Thanks! :)