I have an old Oak(?) floor. Refinished this summer when I moved in (sanded, stained, 5 coats water-based poly). Noticed a small area slightly sunken in. In that area this winter edges of a few of the boards have started chipping away. Looks like it was cut at some point - Maybe an area that was poorly repaired at one time? What's going on and what needs to be done to repair?

3 pictures of the damage are on the video linked below

http://youtu.be/x5jQTqbazfM

Looks like its been sanded down too far. You can only sand a floor so many times before the top of the grooves start snapping off because they are so thin.

that seems to be the general consensus i've been getting. thanks for the confirmation!