Preview animation not matching to in game animation?

Hi,

I am having a very weird issue with regards to using the animator.

So just to paint a picture, i have a character, who is pointing a gun straight. When he runs, the gun and his arms do not move, the only things that move are his legs in running motion. The gun and his arms remain straight regardless of him being in idle or running mode. This looks perfectly fine in preview mode.

Come to being in game, i press A or D, and my characters arms drop a little and his hips rotate a little aswell? So whenever i press "shoot" while running, hes actually shooting more towards the floor rather than shooting straight. Any suggestions why this may happen?

Picture: bottom preview is what i want. Top is what i am currently getting.

Pic
Regards

 

Same HERE ..

 

Is this a bug with Unity? Any dev or with experience know what the issue is? This is very annoying...