Ferroli Optimax HE boiler put in 4 weeks ago. Works for a while then A1 fault shows & have to keep resetting?

urgent help required. Brand new boiler works for few hours then A1 appears and it has cut out. Ferroli engineer says boiler working ok and that it could be a gas or electrical prob. Has anyone else had this... paid a lot of money and still have intermittant heating and water.