I agree that it looks as if the buckling is at sheathing butt joints at rafters.
Roof plywood buckling.
Plywood and osb roof sheathing are the most popular roof sheathing materials in the u s.
Improper installation of roof sheathing panels can result in warping or buckling of asphalt shingles.
Buckling roof plywood below asphalt shingles is a result of many things.
If the adhesive side is not laid properly and not applied flat it will surely show its buckling through the roof shingles.
For a good reason.
Wood expands and contracts so there may not have been adequate planned spacing.
Roofing problems can be tricky to diagnose and solve but the solution here should be pretty straightforward.
Buckling can occur if the wrong type of nails were used to connect the sheathing to the rafters.
When these boards are not properly fastened and nailed to the framing they can.
Most underlayments have an adhesive side and a barrier side.
A roof over or re roof is not recommended because it will certainly lead to buckling.
Your roof decking is the plywood sheets that cover your home.
They are easy to work with readily available and perform the job well.