Hit's not registering damage to Bound target, especially in buildings

I have recently found when fighting boud i am hitting them both with melee and ranged attacks but no damage occurs, I know it's not a low damage issue because after several successive shots i'll do an expected amount of damage. I know the attacks are landing because the enemy will stumble or be knocked prone. i have notices this most often occurs inside prefab structures and points of intrest and is especially common with the sniper bound variant.