Morning guys . A coupe of weeks ago I over boarded and skimmed a lounge ceiling . The customer has just contacted to to say there is a long crack the length of the ceiling . I used 50mm screws through 2 layers of board and boarded across the joists and staggered the joints . I have explained that these things just happen. My house has them . I suggested that he just puts a light filler over it a rub it down. What your thoughts ?