Me think, not enough screws eitherBTW, the plasterboard is fitted incorrectly - it has not been cross bonded with staggered joints
Was gonna mention the screws too - but i'm no expert so didn't like to say - i put screws at 6" (150mm) spacings on all my plasterboarding - especially ceilings. They look like they're at 12" (300mm) spacing to me, unless its an optical illusion??