eco rinse keeps beeping and stops the wash WHY????

I have a simpson eziset 750 and this is only a few months old. The problem is i put the load on and once the machine starts washing this eco rinse button starts flashing and beeping and stops the wash until i go a press the start button again (very annoying) does and one know why this is happening?? I have had the fellow i brought this off back to fix this and he can't find a problem with it. WHY WHY WHY please help??