There are a couple of drawbacks to OSP from an assembly standpoint

One is
that we would get occasional "busts" where the solderability of the pads was
poor on a few pads on the board.

The other area where OSP can fail is with via in pad (VIP) product. If there
is any residue remaining in the holes it will cause a degradation of the OSP
coating.

determine to not be the OSP process at fault, but rather things like unseen
soldermask residues or incomplete removal of the tin etch resist.

Doug, this seems to be a problem with your board manufactures control of the process.

regards

Rich Fudalewski
FCT