After applying a sealant, our installer glued down an engineered wood floor to a concrete base (which he first leveled by sanding it down). A few weeks later, several (but not all) boards began to end-lift. In other parts, tapping on the floor produces a hollow sound. He "injected" more glue to deal with the hollow sound, but more hollow spots seem to be appearing elsewhere. He proposes to deal with the end-lift problem by replacing the problem boards (and will re-apply sealant). He used the best Bostik glue and sealant. I am very anxious that the entire job has gone wrong? Will his solutions work? What is the best way to deal with both problems? Should I be worried??[/b]