This roof was repaired about 6 years ago and is now slowly leaking when there is a heavy downpour. The leak is located close to the center point in between the outer wall and the dormer. It is directly underneath the right hand side edge of the dormer flashing shown below. I'm pretty sure it wasn't properly installed because there is a smaller leak next to the other dormer which doesn't get hit by the rain as hard. How should this be fixed? Is there a short-term laymen-friendly solution to prevent further damage? Thanks.