The crown of a piece of lumber is the upward arch you see when you look down its narrowest edge. In your new home, builders who don't take crowns into consideration can create humps or dips in floors or walls. Engineered wood, floor trusses and I joists can be used to eliminate crown problems.
Buckling roof plywood below asphalt shingles is a result of many things. Wood expands and contracts, so there may not have been adequate planned spacing between plywood boards. Check for proper attic ventilation. A buildup of water vapor is a problem.