Hey Folks 
So I have the player character, I can swap animations end everything works fine. The problem is, I’m using the same model for the enemy, but as soon as I swap an animation, that is not part of the initial animation of the imported model, it seems to completely ignore the weighing of the skinned mesh. The animations I swap are actually made with the same model, but only the animation is exported so I have them as Main@Run.FBX
Any Idea why this might happen ?
Cheers!
Dawnreaver
Something I do not understand from your message is you actually HAVE to export the character and animation as separated data…
This way it is very easy to re-use animation on each skinned models if the skeleton is the same (bones hierarchy + names)
Why would I have to do it ? I can just split the animations right ? The Problem is that either way the mesh gets completely distorted 
Here an image to illustrate the issue:

I imported the character and the animations separately. The skin of the character just starts spinning loosely 
So I had a look at the bones while the game is running and apart from the root bone, the skeleton is all over the place
Well it is rotating out of position. Our Artist did the animations in 3DS Max. do you guys have any idea why this might be happening to the skeleton?
make sure your animations are baked every frame. also make sure you are using the same scale for each all the way through the pipeline.
The animations are baked in Unity. I couldn’t find any difference in the scales. Could the sample rate of the animations in Max and Unity be an issue ?
OK guys so we found why the character was acting strange: the blend mode of all animations was sat to additive, causing the havoc when the enemy character was spawned. Thanks for the support!