Siemens SE25M570GB not heating up – guidance sought please

Hi to you knowledgable folks out there.

My 7-year old Siemens dishwasher is failing to heat up the water, I have done some troubleshooting and would be grateful for your guidance on what I have found and next steps.

The symptoms:

– the wash water is not heating up at all, on any program
– the program does not run to completion, but restarts about half way through (at least that is what it is doing now; we first noticed the fault when unloading the dishwasher at the end of a cycle and seeing that the dishes were wet, cold, and very dirty – coated with a soap/fat emulsion by the looks of it. Since then, testing with an empty washer, about half way through the cycle (intensive) the clock goes back to the start)
– the fault is repeatable
– The washer appears to fill and empty normally

What I’ve found:

I have taken out the control PCB and found a scorch mark and blown joint around what I assume is the heater relay – picture here:

There is also a corresponding black mark on the PCB casing.

With power off (of course) I have put a multimeter across the two wires in the large connector block that attaches to the middle of the PCB, near the heater relay. I am assuming these connect to the heater. The meter shows open circuit.

So, on to my questions for those in the know:

1. Am I right to deduce that the burnt PCB is the cause of the fault? (Looks pretty certain to me!)

2. Does the open circuit across the wires mentioned above indicate that the heater has failed too? If so, is it normal to get two simultaneous failures like that? (Note I haven’t verified that these wires go to the heater, nor have I tested across the terminals on the heater itself – I’m not sure where to find those, to be honest).

3. Assuming it is the PCB at fault, is the board repairable, or does it have to be replaced? I see costs of around £130-140 for this part (ouch)and similar for the heater unit it that has to be replaced too (double ouch).

4. Are there any other possible causes/related faults I should check for before shelling out for a new PCB? I would hate to then find I have another expensive fault that would have meant I would have been better off buying a new machine with 5 year warranty. Perhaps of relveance here is that twice in the last 3 years or so we have had to replace the pressure chamber in the RHS of the machine due to it becoming gummed up, but the symptom both times then was that the drain pump kept running when the sump was empty. That isn’t happening now, and from a quick visual with the side off the chamber looks pretty clear (last changed 8 months ago). But is there any other likely cause of no hot water that I should check while I am at it?

Very grateful for any advice received!