It`s gear assy fault. This is wear and tear sign. It can`t be hammering all the time, just press drill chuck to wall or table or something else and try to turn drill on and you will see difference it`s hammering or not. For that noise it can be two problems one is gear assy and second is when drill stops it stop slow not right after that when you release button. If drill stops slow wen you release button then you need new switch because electronic brake is not working.