Leaves in the Tiles.admin
If there are trees near a tiled roof a common problem is the build-up of debris on the tile gutter that is not seen until the tiles are lifted up. Generally they have to be cleaned out manually unless you get to it with a blower when it is completely dry (more often than not it is moist and muddy).
Generally there will be sarking underneath where the small leaks on all the tiles get thru to and collect in the one spot (due to gravity) , eventually tearing and causing the leak. The flatter the pitch of the roof the more likely there is to be problems with tiles, particularly around trees!