To me, it looks like one of the little cracks that can pop up when you bend in some reflex with a heatgun. It happens in tension rather than compression because the wood is being bent backwards. They look similar to frets but they are horizontal like that instead of diagonal like frets tend to be. Is that a possibility? I worry about those less because they weren't created by too much compression, and they are usually in places that aren't under a lot of stress (the outer thirds).