can scleral buckl fail or the retina become detached again?

Hugh,

Since you have already had a detached retina, it is always possible for it to recur. Usually, once the buckle is done, the repair holds. But, again, it is possible for the retina to detach again.

If you are having the same symptoms as before your buckle procedure, you should see your ophthalmologist. These are such things as bright flashes of light or an area in the visual field like a curtain pulled down.

Good luck.