Try turning the nozzle to either side. Don't hold it at the 6 o'clock but rather at 4 or 8 o'clock.
I say this because this will change the position of the backfeed on the nozzle and may work better.
If hat has no effect i would look for a crimp in the truck fill tube or something blocking the truck vent line coming up from the tank.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles