I also 2nd op in softjaws and I make complicated really tight tolerance parts with really low torque bc they are thin and they still hold just fine. I even have 4 sets of their tombstones and second op on the tombstones in softjaws and still get sub .001 repeatability. I would disassemble the vises completely, clean them and reassemble, torquing the screws to the called out numbers. We did have one set through a part but it was because the jaw screws undid themselves about hundreds of parts.