Buckling can occur if the wrong type of nails were used to connect the sheathing to the rafters.
Roof plywood buckling.
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.
Buckling roof plywood below asphalt shingles is a result of many things.
When these boards are not properly fastened and nailed to the framing they can.
Wood expands and contracts so there may not have been adequate planned spacing.
They are easy to work with readily available and perform the job well.
Most underlayments have an adhesive side and a barrier side.
The nails slip out of the sheathing and create small visible bumps on the surface of your roof.
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.
Improper installation of roof sheathing panels can result in warping or buckling of asphalt shingles.
Your roof decking is the plywood sheets that cover your home.
A roof over or re roof is not recommended because it will certainly lead to buckling.