In my travels as a saddle fitter, I also look at the bridle as well. I am seeing crown pieces that are way too tight. You should easily get your thumb under this piece. When you ask for collection, this part of the bridle tightens and the pressure increases.
Try putting your fingers under the crown piece then ask for flexion and you will see how much it tightens. A horse's brain stem is not too far under this piece. Along with the ligament structure that holds up their neck. And where occiput and atlas join which is highly innervated.
Needless to say, adding pressure to this area is horrible for the nervous system, and skeletal system. Lengthening the cheek piece of the cavesson part of your bridle even just one hole (if it is so tight that you can't get a finger under the crown piece) will relieve pressure here and will not lower the nose band.
You also want to make sure the brow band is long enough to clear the back of the ear by a couple of inches. I also see brown bands that are too short and cutting into half of the ear and cramming the cheek piece into the TMJ.
If the first thing your horse does when you stop riding is rub his face on his leg, this could be a sign that your bridle is pinching some nerves. Usually this is a sign of numbing and tingling in their face from nerve compression. I see this a lot. In fact probably the majority of horses that I see.