I'm not a doctor, i'm a lawyer, i work with surgeons and i know all about the lap band process, i'm here because this is a page that i recommend to our patients.
If you follow your diet instructions then the slippage was not your fault, the band it's desing to be in your stomach and take a lot of preassure, if the doctor put the correct preassure and the stitches that are necesary even if it is a lot of years the band don't slip, one thing that could happen is maybe that the band was not a god one, but it doesn't slip for natural causes unless you eat something in bad conditions and you vomit a lot.