Neff dishwasher S41E0S0GB/18 Heating problem after changing heat pump assembly.

I would appreciate any thoughts on the following problem. After changing the heat pump in this machine (For open circuit heater), customer now complains that it “isn’t as hot as it used to be”. I checked the temperature of the wash cycles and indeed, although it is heating, the 45deg quickwash cycle achieved 30deg C on each phase (Wash, Rinse and FInal rinse). A further check on the initial wash on a 75deg wash achieved 56deg. I didn’t wait for it to finish the cycle but customer tells me that it is not steaming hot at the end like it used to be.

I have two areas of concern.
1) I replaced the original wash/pump with part number 12019637 – the Neff site lists 00651956. (Connections listed the part I fitted as a cheaper alternative.) Could that cause this problem?
2) The plug on the circuit board with 2or 3 red wires plugging into the left side of the board. The top socket and the next one down will both accept his plug. I’m sure I’ve checked this in the past and the two sockets were in parallel, so making either a suitable choice. I chose the top socket. Could this cause the problem?
The fault seems to lie within the temperature measurement circuit Could the pump I fitted have a different value sensor to the recommended one?

Any thoughts or solutions would be greatly appreciated.

Graham