i have crohns disease & had to get clearance from my Gastro Dr.,
in fact my LAP-BAND® Surgeon & Gastro had a con call before i could get cleared for surgery. apparently it's not a recommended surgery (LAP-BAND®) for those with abdominal problems & previous surgery.
since my issue with crohns have been managed for 10yrs with diet vs drugs - i was given the OK. to date, i've not had any flare ups. i think the LAP-BAND® actually has helped with keeping my diet in check.
not sure your problem - but i suggest a healthy honest conversation w/your LAP-BAND® surgeon so he knows what he's dealing with.

ps - productive burp is when the food is just not going to go down, and well it comes back up & fast...