Vokera Unica 28 HE error code 01?

When boiler set to economy the boiler appears to have a mind of its own. It does not respond to the thermostat. Requests from the thermostat to the boiler are not registering and other times when a signal is sent for the boiler to turn off it doesnt respond. when the dial is fully clockwise (heating and water on constant) the central heating does not respond. At no time is there an issue with hot water on any setting. When boiler is reset and powered on again the red light illuminates for a few seconds and the error message 8.8 and 01 are displayed. Please could you help? Many thanks