Here are 2 more photo’s of things to watch out for. Another window that is now in trouble of future moisture problems because of the garage addition, and when the shingles were added or replaced, they didn’t flash them to the main house in a very good way to keep the rain water flowing down and away.
The corner where the shingles, the trim board, and the window meet is almost guaranteed to be a problem area in the future. Every year water is going to run down the siding, and run down the roof and get to that window. And beside being something nice to look through, a window is also a hole in your wall. It is already an easier place for water to get into the building, without directing the roof right to it.
The second photo shows how the rooof meets the siding of the main building. Between the shingles and siding there is just enough room for water to get under there and possibly get down into the roof decking or the wall behind it.
I also see that the way they tried to seal this trim board was with a bead of silicon and that is pulling away now as well. A preferred way to meet the shingles and siding would be with step flashing. As the roof was shingled up, step flashing should have been installed. Step flashings are small pieces of preferably galvanized metal with a 90 degree fold in the middle. Half the metal goes on top of the shingle below and the other half goes up the wall. These are stepped up the roof with the shingles. Then in this situation, all but the bottom inch or so of this flashing would get covered by the trim board. The lower inch or so is left exposed so that nothing is there to slow the drainage of the water off the roof.
If there is not much of an overhang above this trim board and it would be getting the brunt of a lot of weather, the top of the board could also have been beveled – had an angle cut on it , to help rain coming down the siding to keep draining off and not catch and sit on the trim or go behind it.
Try to avoid anything that will stop water from flowing off your home. Any moisture sitting for periods of time on any part of a building is a potential problem.