Something is overriding my animation but I can't find it...

Hi, I started a project and I have using this asset: https://assetstore.unity.com/packages/templates/systems/3rd-person-controller-fly-mode-28647

I created a new animation "aim" and made the transition from Idle to Aim when the user right click. The problem is that the animation start and loop in the animator but when looking at the scene, the character start the animation but immediately go back to the Idle one even tho the animator continue to loop the aim animation. If I set the bool value of "Aim" to false, my character start doing the aim animation like I want. So I thought that some script were messing with the animator, I disabled all the script of the scene but the problem remain.

Here is a gif showing the problem: https://gyazo.com/beffd7e48245219c67a09690d9117e6e