I keep having the same issue with my short pastry. When blind baking the sides overcook before the base is cooked. I used to think it was the inconsistent temperature in my gas over as it was usually under temp so had to bake for longer but have not switched to an electric oven and have the same issue. The texture is fine and the pastry is still crumbly but the sides always go very dark brown before the base is cooked. so i need to leave more of an overhang of pastry so the sides of the tart cases are further away from the edge of the pastry?