Vomiting is an often reported side effect after Bariatric Surgeries. In the immediate post-operative period, this is common and usually due to the rigidity of the stomach following surgery and sometimes due to side effects from the drug used during the surgery. This should not go past 48 hours.
Persistent vomiting beyond 48 hours could be due to a problem that may require intervention either in the form of an Endoscopy or further surgery. If the operation has been done correctly by an experienced Surgeon/Team, then vomiting of this kind is extremely rare. In my practice, we have only encountered this perhaps once a year and have not had a need for any interventions.
Vomiting which persists for weeks and months after the surgery is a clear sign that there is something wrong with the operation and warrants appropriate investigations in the form of Endoscopy and special X-rays /CT scan, followed almost certainly by a revision of the operation.