Roof sheathing impressions ins roof

Looked at a new construction home today. When inspecting the the roof I could see the outline of the roof sheathing through the shingles.
From the attic, the sheathing and structure appeared to be adequate with sufficient ventilation and insulation.
Any ideas about a possible cause or reason?
Could it be the sheathing got wet and swelled at the ends before the shingles were installed?

That’s my impression, sheathing got wet during construction and the edges swell.

Read this thread.

Thanks, I don’t believe I have seen this before, at least not this evident

yes to all of the above, who ever roofed this should never roof again imo…they should have never roofed over that!

Good video about OSB edge swell, the reasons for it, and new products that resist it.

That’s not necessarily “edge” sagging but can be the result of uniform panel expansion due to moisture absorption. It’s actually more common on new construction. The plywood panels leave the production line at about 4% moisture content. The bundles of sheathing get wrapped in plastic and put on a train, then to a lumber yard somewhere, then to a jobsite. If they rip off the plastic, install the sheathing right away and then install shingles soon afterwards, the sheathing has not had time to reach equilibrium moisture content with the jobsite environment. If the jobsite is more humid than 4% (which is it almost everywhere) the roof sheathing is going to absorb moisture from the air and expand. Shingles installed on sheathing that expands will buckle where they bridge panel joints.
Dunno about that sagging section though… looks like bad work.