Every horse responds differently. No matter the response it is important to release the pressure only when the horse tries to do what you are asking and not to change what you are asking while the horse is trying to learn what you want.
The first horse is resistant and not comfortable. By moving with her and continuing to ask her to lower her head and releasing the pressure when she tried it gave her the time and freedom to learn what was expected of her.
What a contrast with the second horse, who was willing to try and comfortable with dropping her head and flexing laterally right from the beginning. This was the first session for both these young horses. After each one understood I moved on to the next exercise. I will start each session with this exercise until each horse has a clear understanding of what is being asked and will drop their heads and flex laterally willingly.