This just comes with the territory with the band for a lot of us.
Your diaphragm keeps your lungs and upper respiratory organs separated from the stomach and gastro organs. That's the culprit. The band either presses up against the diaphragm (and the Vagus nerves run through there) or the top portion of the stomach presses against it.
If you continue to get htis pain and simply leave the band, there's a good chance the nerves will become damaged, leading to permanent pain. I had my band removed over 6 years ago due to the chronic complications I experienced and I still get occasional left shoulder pain because I had so much damage to my diaphragm.
Take care. I hope you can get it all figured out and be pain-free.
Avoid kemmerling, Green Bay, WI