loooked at 15sbi boiler today (lpg)which is aparantley locking out now and again but starting up again after reset button is pressed.As usually happens wouldnt lock out while i was there but burner would not ignite first time every try/flame would die down within a couple of seconds then it would try again and ignite so im asuming that sometimes it fails twice then goes to lockout-tested pcb and resistance on gas valve seems fine.I changed the setting on the softlite dial on the gas valve to the 24sbi position-this then gave more gas at startup boiler the ignited everytime without fail anybody come across this prob b4?Im thinking either faulty gas valve or flame sensor.