You don't indicate if this problem is suddenly happening or has been happening since you started trying to fill the tank.
If it is a sudden change, then check the filler hose for a broken support/tie. Also, look at the pumps from which you're filling. Are they a different style than your pumps at home? If so, it may be the pump causing the issue - in this case, try changing the angle of the pump while filling, slow down the fuel speed while filling (hand hold the pump at a slow speed instead of using the pump lock), etc.
If it has been going on since you got the RV, then check for a kinked or deep bend in the filler hose (many RVs have a deep bend in the filler hose to maneuver around tanks, etc.; these bends can cause fuel to "spit back" when filling too fast).