I'm still having considerable trouble with this. I have read the manual and your (Umberto) previous notes repeatedly, and yet the refuelling truck gets called automatically a 2nd time once boarding is complete.
So, just to be clear, I am flying the PMDG 737-800 in MSFS.
1) Per your guidance, I have "Detect custom aircraft system refueling" DISABLED and I have "Always refuel Progressively" Enabled.
2) I start with a small initial quantity of fuel onboard.
3) I call the GSX fuel prior to calling for boarding. Once the fuel truck is on its way, I commence boarding, to get the pilots and crew on board and perhaps the first few passengers.
4) Once the fuel truck arrives, and once prompted by GSX, I set the desired fuel for my trip in the FMC, which is higher than amount set initially in step 1 above.
5) Fuel truck completes the simulation of fuel going in, as expected.
6) Boarding completes, both passengers and baggage.
7) GSX then announces that the fuel truck has been called and is on its way again! I then have to wait for the whole process to complete, including adding more fuel via the FMC in order for GSZ to register that I've added fuel...
How do I stop this? Is there a shortcut key for calling the GSX fuel truck that I'm unaware of but inadvertently clicking? Could it be caused by interference from other add-ons (I have Navigraph in-game charts, and SHIFT-Z stats installed)?
One point in your previous post which confuses me, and appears to be contradictory to your later point is where you say "[the manual] says with the "always refuel progressively" just CALL the GSX Refueling automatically whenever a fuel increase is detected, but that doesn't change the fact you still have to refuel manually.". This implies that whenever GSX detects an increase in fuel, it calls the GSX Refuelling automatically... In which case, if I follow the steps you've set out, and increase the fuel in the FMC as you've indicated, and once prompted to do so, is it this increase in fuel which then triggers a subsequent GSX refuel? I simply don't follow the logic, but perhaps I'm yet again being thick and don't understand.