I have two Focus cars, one does this sometimes and the other one never. I've pulled tanks to work on pumps and know for sure nothing wrong with hoses.
All I know is that the one with the issue fills fine if I twist the gas nozzle about 120 degrees to back of car where it is getting close to straight up, it then fills fine and every time, go figure.
In my case I'm pretty sure it has something to do with fuel/vapor stacking up right there where it's being discharged from hose to trip the gas hose shutoff. Once you angle the flow to sluice smoothly down the inside of pipe then the area stays clean enough of vapor to not trip.
Try filling at different angles from what you normally use by swinging gas hose around to different positions, that's how I found my sweet spot.