Gas space heater - not working properly (East Hendred OX12)

This is a Draper PSH300, 70kW (238,80 BTUs) propane gas space heater. It runs from a propane gas cylinder (orange not blue) and the regulator at the end of the gas hose screws into the gas cylinder with a left-hand thread. It also needs mains power to drive the fan. The fan works perfectly but the flame doesn't always run properly and it makes a screaming noise (much like the fan bearing has gone but it hasn't). The supplier says that you can't get spares for it anymore so we have purchased a new one. I wonder whether if it was stripped down there might be a simple fix, maybe not. Sometimes it runs correctly for a period and then the flame reduces and the 'screaming' starts. The gas hose looks fine but good practice would dictate that it should be replaced now. We are in East Hendred.