Hi there, We had an inset log burner installed and the installers did a great job. Then three month later the fire board cracks from the join in the boards up from the fire. A month later they turn up and fill the crack with normal filler. They drill holes in the fire board and squirt expanding foam in. We’re told to leave it 24 hours which we do. First fire it cracks in the same place. I’m wondering if drilling holes reduces fire board efficiency? Could a normal plasterer pull it down and re-do it? Should they pull it down and fix it?