We use two DeWalt miter saws to cut our frames and they have special blades to cut molding in them. We have been having a problem with gaps in the middle of the joint no matter how hard we press the corner together. The gap is only on the top face of the corner and not all the way through. This only happens on our flat molding and is not much of an issue on different kinds. We think it might be a problem with the saws but don't know how to adjust them. What can we do to fix this? Any help with this would be much appreciated.