The pommel is too low creating pressure on the withers. Above is a horse showing white hairs on the withers from a saddle being too close.

Pommel High

The narrow gullet is pinching the horses withers. It is also lifting the front of the pommel, and creating too much clearance. The seat is too far back.

Channel through the back of the saddle too narrow - only 2 1/2 fingers wide, which is sitting each side of the spine and pinching. The space needs to be around 4 fingers.

Saddle channel too narrow sitting close to the spine. This will restrict the horse from bending and cause hollowing in the back.