Bead sights ,especially those that are pressed or glued in do come out when barrels are reblacked. They also tend to disintegrate in the boiling water and when being "brushed" off between applications of the blacking chemicals. Although care is taken it is not always possible to remove them without damage and to refit them after wards. I always advise customers that we take no responsibility for non metallic sights when reblacking.
As to the Vibration ,its impossible to pass a serious comment without examination. Is it in fact a "vibration" or a "rattle"?
Try it with the extractors and pins removed.It could be one of several other things , do the barrels ring when tapped? Or are they dull,dose it have a center bead? Etc.
