Problem with Worcester Bosch Greenstar 38CDi Classic ERP Boiler?

We had a Worcester Bosch Greenstar 38CDi Classic ERP boiler installed at the end of July 2015. We keep getting EA 56 fault. The regulator on the meter has been changed and a new bigger gas line put in. Worcester Bosch have been out twice, changed the electrodes and now have just changed the bearing plate. Our plumber is an accredited by Worcester Bosch. He has checked everything but is baffled by this boiler. We have a Comfort 11RF Thermostat and receiver. Could it be that the comfort 11 could be at fault. The Worcester Bosch engineer didn't know anything about that part. Fed up of finding the boiler off in the morning, although last time it went off it was 3.54pm and the boiler is set to come on at 4pm. Any ideas?