How does a gastric sleeve slip?

It does not. Gastric sleeve is surgical weight loss procedure in which a major portion of the stomach is removed along the lesser curve of the stomach. This leave a banana shaped stomach. Unlike gastric banding where a band is applied along the top of the stomach, the gastric sleeve is not associated with slippage. I hope my answer is well descriptive.
Bands slip. A gastric sleeve is a procedure where you remove 80% of your stomach making it into the shape of a shirt sleeve (hence the name). So there is nothing to slip. A gastric band on the other hand can slip. It is usually the result of a hiatal hernia that causes the slip. A slip can usually be fixed by repositioning the band, although sometimes the band has to removed.
Sleeve gastrectomy . It doesn't. There is no slipping in a sleeve gastrectomy. That only occurs with the lap band. .