Hi. The most common cause would be an incision site hernia which is fairly common and is usually easy to diagnose. Sometimes it is obvious to see when flexing the abdominal muscles, otherwise an ultrasound will detect it. I had my GB removed in 2004 because they thought it was causing pancreatitis. They sent me home the same day after surgery and I had to go back by ambulance that night as I was blacking out. I was bleeding internally and lost 7 units of blood. I healed after a transfusion and 7 days in the hospital but it didn't stop the pancreatitis. After 7 years of pain and lots of endoscopes a tumor showed up in the tail of my pancreas on an MRI. A different surgeon started a laparoscopic distal pancreatectomy but had to convert to a full open procedure and removed half the pancreas and spleen. The operative report showed I was full of adhesions and fibrosis which caused the doc to convert from lapro to full open. This was probably caused by the blood loss of the GB surgery. The surgery did stop the pancreatitis but about a year after surgery I've had incisional pain but only to the left of the vertical incision. They ruled out hernia and the surgeon won't see me saying there is nothing that can be done. My now third GI doc is an old timer who is somewhat irreverent of the surgeons and said that there can be nerve damage that doesn't show up on an MRI or ultrasound. However I can't find a doctor that treats nerve damage. This link has good info:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5908491/