Hi! I have run into a similar problem. After sanding a luan door, I have a large spot and a few smaller spots that do not take the stain like the rest of the door. It seems that there is a thin veneer that is easy to sand through. Maybe there is a way to 'patch' these holes in the veneer so that it will take a resonably uniform finish. This problem is maddening and I do not want to buy anoher door due to custom doors & sizes for our home. Any ideas out there? Thanks!