hello all i've just been to the house where i did a smooth render job an i noticed some hair line cracks and where the cracks are it sounds hollow so it's safe to say that it hasn't bonned in those areas am wndering why it's happened and the other half of the house which another plasterer did has done the same and he's just had to put it right and i know it's only time till she picks up on mine any ideas why it's happened ??? and should i need to go back to repair it what would be the best way