2nd Driver Won’t do Full Fuel Stint

[RotaryRacer787b]

Having an issue in endurance races when the 2nd driver won’t do a full fuel stint. When I change at the pit stop to the AI, they often do 1-2 laps or at most a half tank. Any idea where to adjust this? I can manually cancel the pit stops sometimes, but if it’s last minute, they stop anyways.