Face pull mistakes, faults and checks
If you are unsure which muscles a face pull should reach, check the weight first: too much makes you lean back, hands the load to your lower back, and leaves the rear delts, upper back, and rotator cuff without the intended work. Keep the cable light enough to control, because once your torso has to help finish the pull, the exercise has changed. A face pull is a controlled cable pull toward the face, with the upper arms high and the hands turning back at the finish. Dropping the elbows and pulling low changes it into a row and removes the shoulder-rotation part.
Faults
The leaning-back fault shows up when the cable pulls you forward, your torso moves backward to finish the repetition, or your stance gives way. The load then shifts to the lower back, and the smaller target muscles do less. Use a lighter cable, stand tall, keep the repetition controlled, and pull toward the eyes with the hands finishing beside the ears.
The low-pull fault appears when the rope ends at the chest or chin, the elbows drop, or the hands fail to turn back. The path misses the external-rotation action, and the shoulders can finish rolled forward and raised. Keep the elbows high, let the hands reach the end before the elbows, and rotate the hands back as the pull finishes.
Target muscles
The intended feeling is in the rear delts, with the upper back assisting the shoulder-blade squeeze and the rotator cuff contributing to shoulder rotation. That gives you three parts to check when the repetition is under control: the rear of the shoulder, the upper back, and the turning action at the shoulder.
Once the fault is gone, the movement should resemble a reverse fly with a shoulder turn and shoulder-blade squeeze, rather than a shrug, an arm pull or a row. Use that comparison during the set. If the shrug or arm pull takes over, the target muscles are no longer giving you the clearest signal.
Professional assessment
A physical therapist or certified trainer is the appropriate professional to consult when the lower back hurts.
Next set
On the next set, watch one repetition from the side and check that your torso stays tall while your hands reach the end before your elbows; if either check fails, reset the movement with a lighter cable.