There are many issues with the SP system. I have a AKL MEL flight later this week which was booked as Works and which I've oneupped to PE Spaceseat. When the oneup came through the SP + APD earn both dropped in the potential earnings screen to be both lower than lowest estimated Works earn. Interestingly in the Last Minute Tips before your Trip email which I received today the SP was higher than in the original booking.

I've had this happen before and contacted Air NZ and they reversed the incorrect lower earnings and credited as per initial booking - so after this trip I will likely have to do the same to get the correct earn.