Gas Boiler keeps cutting out twice a day

The gas combi boiler keeps cutting out and requiring myself to top it up twice everyday, a new wireless digital thermostat has been fitted, no leaks are found at the radiators, a new expansion vessel has been fitted, no water has been dripping down the downpipe from the boiler, an anti - leak seal has been poured down one of the radiators twice in the space of 6 months, the boiler has been serviced and no problems found. When I check the pressure on boiler it reads 0.6 to 1.0, then it cuts out. Any ideas on what the cause of the boiler cutting out everyday is and how to get the problem resolved? thanks