greenstar Ri flashing?

hi. have a greenstar ri about 5 years old. problem is it keeps going off and needs constant resetting - about 5 times a day. plumber been round and tried change timer and checked electrics but it still goes off after a while. the blue light is either intermittent or off or even steady on but often its on but the boiler is not fired up. it can't be frozen pipes like many people have talked about because its lovely warm weather. Any suggestions most welcome.