I want to repaint a interior window ledge of a bay window. Unfortunately after rubbing it down and removing much of the old paint, I found that it's made of ply-wood and the top layer in places is a bit springy to the touch. My guess is that over the years, perhaps assisted by water ingress such as condensation from the windows, the top layer of ply has partly come unglued from the rest of it. Replacing the whole window-ledge would be a big job, so would prefer a quicker fix.
I've pushed a thin blade through cracks in the top layer and it seems firm underneath, so it's probably just the top layer that's a problem. It would be nice to re-attach the top ply layer to the substrate before repainting. I wondered if I could bore a few small holes in the top layer, funnel some glue down and hope it could be persuaded to spread out enough to re-attach the layers if it were to be weighted down firmly. But I'm not sure if this would work or what glue to use. Any ideas?