This can be a sign of adjusting the crop, where food and water are stored before moving on to the gizzard for digestion. It is common to see this, but it should not go on and on. Sometimes a crop impaction can occur if they have eaten something large or something like grasses or straw that gets wound up and won't pass. Gapeworm can cause severe gaping, but if they are not having severe distress breathing, and can eat and drink, it is probably not gapeworm. Gapes can only be seen inside the dissected trachea or airway after a chicken is dead. Gapeworm can be treated by giving fenbendazole (SafeGuard liquid goat wormer or equine paste at 1/4 ml per pound of weight for 3-4 days in a row orally. Feel of the chicken's crop in early morning when it should be empty. Here is some info to read about impacted crop: https://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
