Neff d/w not washing properly

From UK, 1 post

What I know about dishwashers - unless they're yellow, come in pairs and are called Marigolds - can be written on the back of a greasy teaspoon. So any useful suggestions would be much appreciated.

My neighbour's dishwasher died a month or so ago, so an engineer was called. He was very thorough (definitely not a cowboy) and diagnosed a u/s PCB which was subsequently replaced. The machine appeared resurrected: all the lights came on and things appeared normal. But 3 weeks later my neighbour told me that, although the d/w seemed to be working - i.e. it would go through a wash cycle with relevant hissing and swishing noises - nothing came out clean, or had since it was 'fixed'. When I checked I found the water wasn't heating up. And sometimes, he tells me, the soap dispenser doesn't open.

I phoned the repair company who say that their engineer would automatically have checked the heating element but they'd be happy to come out again and check for the problem. If their parts or workmanship were at fault they will get it sorted foc. But if it proves something different, they'll charge their normal £35+VAT diagnostic visit and thereafter it would be up to my neighbour whether he went ahead with further repair, depending on the fault. As he's already spent £210 (roughly half the cost of a new machine) he's naturally sucking his teeth at this.

Any thought or suggestions as to what might be the problem? Is it likely to be related to the new PCB and therefore covered under the guarantee - or is that like asking how long's a piece of string?