I think were all shooting in the dark here (no pun intended) but along with Thunderbird+'s good suggestion, I have found that woodpeckers are quite wary of owls. It wouldn't cost much to find one of the shiny foil owl cutouts at a DIY store. It's their profile that scares the woodpeckers and the ones I've used are about 18 inches tall. They're meant to be hung where air currents will cause them to ripple. I've used colored (matching the wood tone) all weather spackling to good affect to fill the holes left by your visitor. It can be finished to get even a better tone similar to the wood you are using. It could be that the mating season is still going on and the woodpecker maybe drumming for territorial purposes rather than seeking bugs that have bored into the wood. If that's the case, perhaps it will end soon. At any rate, best of luck!