I've repainted the master bedroom with a B&Q "colours" matt paint, which is OK apart from half-way down one wall. The paint there has cracked, almost like a dried river bed, and no amount of coats has cured the problem. I've sanded each coat down, and also tried adding pva into the paint but each coat dries cracked.
Does anyone know what it wrong? The cracking only appears at dado-rail height and below on one wall.