Hertz Firematic 199

Wondered if anyone has had an issue with the stoker auger on this model when using hardwood chip e.g. from hedge laying . Motor really seems to struggle with this material , though it is well within the G 30 spec .
I have had the system switch off on numerous occasions with Motor Protection Fault as well as the chain drive pulling itself slack for no good reason other than the hardness of the wood, as far as I can see . On this particular boiler the motor in question is 3 phase and run through a single to 3 phase inverter drive ( Power Flex 4 m ) . I have heard that similar Hertz boilers running on 3 phase supply can auto reverse stoker auger in conditions of high resistance in order to free up auger and clear any possible blockage . Does anyone know if is possible to set up my boiler to do this as it would be the obvious answer I think ?

Its not wet fuel as that issue is sorted , I will check the grate speed though . Seems ok using softwood but hardwood causes issues , very frustrating really as I think it should be able to cope with this .

yes