Animator in prefab does not get initialized

Hi,

I have units as prefabs, each with an animator and an animator controller. The controller has 4 states, and 3 layers changing the animations of each state. When I spawn a unit, I get the warning "Animator is not playing an AnimatorController". The trouble is that I try to change the weight of the current layer, but the layerCount property give me 0 and GetLayerIndex(name) gives me -1.

I gather something is wrong with the prefab or with the controller. So far I tried to create an empty controller: same result and to move my prefab from an assetBundle to the Resources folder: same result.

I also tried to do a SetActive on the gameObject once instanciated, do a anim.Play and so on, without luck.

Do you have any idea ?

Thank you