Toyota LandCruiser: LPG refill problem

I can't refill my 1998 dual-fuel Toyota Landcruiser any time it's over 30-degrees C. A friend who used to be in the LPG industry said to have a larger fill hose fitted, but it turned out that I already had the largest hose. The automatic fill limiter was adjusted and I was advised to fill at petrol stations with aboveground storage tanks on hot days, but it still won't fill when it's over 30-degrees C. Another friend said it could be air in the tank that needs to be removed. Do you have any ideas?