There is a revised PCB now for the SUPRIMA.
Storage conditions can cause corrosion in PCB's at solder joints, just moisture to blame, activating residual flux.
I now have a Potterton Promax 28HE+, which I am assured is about as good as you can get at the price.
I would have preferred a Worcester Greenstar, or a Megaflo type system, with stainless-steel condenser in the condensing combi.
The Scottish Executive grant system gives people no choice in this respect.