Inflammation of gizzard in large broiler birds

it is called Pendulous Crop. this kind of Case do occasionally occur in poultry farm. One out of 5000 bird might have it. the cause is unknown but i want to assume it is a nervous issue i.e issue with Vagus Nerve.

Mareks disease virus infection affecting peripheral nerves especially branch of vargus nerve supply to the crop could lead to pendulous crop. Crop impaction due to roughages/undigestable feed is often seen in turkeys causing pendulous crop

As per my knowledge in poultry particularly impaction of crop or infection in crop and sometime air sac formation under the skin due to hearted skin. It may also vagus narve paralysis of crop, so many reason it seem like.