Mecanim add weight to certain animations

I have an attack animation. This animation needs to play no matter what, over all idling and walking. I made an AnimatorController that controls the idling, walking, blocking, and attacking. A variable, isAttacking, controls when the model plays the attack animation.

The attack animation works - it plays when you are idling. However, when you are walking, most of the time it doesn't play.

Here's the AnimatorController:

And here's (the important parts of) the script that governs it (Boo):

     import UnityEngine
     
     class PlayerAttack (MonoBehaviour):
     
         private animator as Animator
     
         def MeleeAttack() as void:
             animator.SetBool('isAttacking', true)
             Invoke("StopAnim", 0.1)
     
         def StopAnim() as void:
             animator.SetBool('isAttacking', false)

To make the attack animation play no matter what, is there a way to add weight to that animation specifically?

If not, is there a workaround?

Thanks in advance