frequent shut off of gas pump on 2001 Subaru Impreza

When I pump gas the gas station pump frequently shuts off in the process. I replaced the Filler Pipe, Valve and flange nut because these parts were rusted. Cost $306. The problem persists. Did I throw $300 down the drain ?
What can be done to fix the problem ? One answer posted said to replace the roll-over valve. If that is the one at the end of the filler pipe, I already replaced it. I know of no other valves related to gas filling. Can anyone please help me solve this mystery ?

Asked by for the 2001 Subaru Impreza
Hello, has the mystery been solved? Was there a vent for the evap system that was plugged?
Thanks for the update, sometimes we just have to deal with these type of things.
The mystery has not been solved but I worked my way aroundthe problem. It wasn't plugged, I insert the gas pump at an angle and the problem goes away.