I thought it might be as a result of having the APU started while refueling (causing the fuel truck to arrive twice) but I tested this morning with no APU running and the fuel truck arrives a second time. Here is my sequence:
1. request fuel
2. request boarding
This time the duel truck would not leave, with the resulting voice prompt of "set your aircraft fuel quantity" playing. It would not let me push back until the fueling was completed.
Can this be fixed or can you have the option of cancelling the fueling at any time?