We have beautiful 8 inch (actual width) old generation heart pine floors - the stuff reclaimed and milled from old textile mill timbers. They are installed over 3/4" plywood sub-floor with a 30# roofing felt vapor barrier. There is a full daylight basement underneath the main floor where the heart pine is and it is a fully conditioned space. The floor has been down for almost a year now and has been finished (Waterlox Original) for over six months.

When we walk on the floor, you can hear the planks sort of "smacking" for lack of better words, against the vapor barrier in places and when we walk across a butt joint, you can fell the joints move a bit in certain places. I was on-site for most of the install and the nailing was adequate but the ends were not matched and they did not join the ends with a biscuit joiner. There is no visable cupping going on either.

Any sage advice out there on the best course of action (if any)? Some face nailing or screws with pegs? Or is this just par for the course for an antique heart pine floor?