Shen Taunt Bug

I have been playing a lot of shen recently and I have notice a potential bug that hurts his play tremendously. There are instances when I will gank a lane or even ult an ally and when I taunt an enemy champion it gets ignored and the enemy is still using abilities on my ally. Why is this happening when shens taunt is one of his main moves for engage. I have taunted jax's and they used their jump immediately after I taunted them, same goes for Jayce and many other champions.. Please just take a look into in.