Roof Plywood Buckling

Improper installation of roof sheathing panels can result in warping or buckling of asphalt shingles.
Roof plywood buckling. For a good reason. The nails slip out of the sheathing and create small visible bumps on the surface of your roof. Most underlayments have an adhesive side and a barrier side. They are easy to work with readily available and perform the job well.
Buckling roof plywood below asphalt shingles is a result of many things. Your roof decking is the plywood sheets that cover your home. I agree that it looks as if the buckling is at sheathing butt joints at rafters. Check the buckling pattern for spacing at 4 or 8 ft intervals or a multiple of that.
Roofing problems can be tricky to diagnose and solve but the solution here should be pretty straightforward. Plywood and osb roof sheathing are the most popular roof sheathing materials in the u s. Wood expands and contracts so there may not have been adequate planned spacing. But they must be installed correctly.
A roof over or re roof is not recommended because it will certainly lead to buckling.