Can lap band cause a A small hiatal hernia and your diaphragm?

No, A hiatal hernia can develop in people of all ages and both sexes, although it frequently occurs in people age 50 and older. Hiatal hernia occurs more often in overweight people and smokers. The most common cause of a hiatal hernia is an increase in pressure in the abdominal cavity. (The abdomen consists of the lower part of the esophagus, stomach, small intestine, colon, rectum, liver, gallbladder, pancreas, spleen, kidneys, and bladder.) Pressure can come from coughing, vomiting, straining during a bowel movement, heavy lifting, or physical strain. Pregnancy, obesity, or extra fluid in the abdomen can also lead to a hiatal hernia.
A common complication of the Lap Band is GERD. Acid reflux can be triggered by a tight band. This causes a problem. When the band is tightened it may trigger acid reflux. When its loosened, the reflux goes away but there isn’t enough restriction to cause appropriate weight loss.

Yes, it has been shown that gastric bands are associated with hiatal hernias.  Most hiatal hernias do not cause symptoms, specially small ones.  If you are getting acid reflux, difficulty swallowing, these symptoms are likely caused by the band not the hiatal hernia.