I had a new roof done 2 years ago. Roof isn’t pretty, uneven slate tiles. Had about 4 slip in the first 6 months. The pointing in the ridge tiles keeps falling out. I’ve spoke to the roofer and says nothing wrong with it and says it’s a problem with pointing ridge tiles onto slate. Yet rest of my street have older roofs and pointing in tact. I think he’s put a bad mix in.