NEFF S5456X2GB/42 Cycle Never Finishes

the washer runs the desired program but does not complete , it remains on 1 minute left , on most occasions the dishes are washed okay, but you have to open the door each time as machine never bleeps. On the odd occasion it does work its on the quick rinse cycle. Had the local NEFF approved engineer out and he fitted a new control unit and that didnt cure the fault, on the 2nd occasion he cleaned out the pipes and then thought i might need a new pressure chamber, module and heat exchanger as the machine still isnt working correctly .Is he close to getting to the root of the problem ?

thanks for your help