Hi hope someone can help. Have had 2 plumbers in to look at a Maxol combi. Boiler cuts out whenever the shower is turned on and fault no 6 is shown. CH works fine, bath lukewarm while radiators are hot. Its just been looked at by an engineer who said there's nothing wrong with it. Previous plumber fitted an independent pressure tank . It worked for one night!! The system was recently power cleaned and was v sludgy but worked a treat after. Now this which means no showers or baths... what the heck is going on?