This is a common problem on older roofs. The ridge caps in this small "bend" are cracking from the stress. If the roof is installed right, these don't occur early on so easily, but it's unavoidable as the roof gets older.
Can't See It?
Neither did we, until we investigated under the roof in the attic. The leak is in the dead center of this photo!!
This underlayment has holes in it, and we don't repair roofs without fixing it properly.
The holes in the underlayment have been covered up with a peel-and-stick heat-activated upgraded underlayment.
Sometimes, a patch can save a customer thousands of dollars. If the roof has several years of life left on it, why replace it? Might as well spend a bit now to keep the roof in good condition.