Gee, John, you got lucky. Easy problem and solution. The problem is humidity. The solution is a long drywall screw. From the point of maximum rubbing, just run a 3 or 4" screw thru the stile and into the framing behind it. You can countersink if you wish but the screw will probably seat itself flush as you will want to tingten it down enough to pull the bow out. You might want to have a long straight edge so you can check that you are just pulling the stile back to true and not putting a reverse bow in it. It will be a lot easier on you if you do this with a power driver. Henry