Gas at the Pump, or Not

There's something odd happening with some gasoline stations.  I think it has to do with the pump pressure detector/setting, whatever it is that detects a full tank and makes the nozzle "click" and stop pumping gas.  I've discovered that with certain gas stations the nozzle "clicks" even though I know the tank isn't full.

Example.  I was at a Sunoco with about 1/5 left in the tank.  The first "click" happened after 2 gallons.  A full tank is 14-15 gallons.  From 2 gallons on filling up was torture.  Every couple seconds another click.  It didn't matter how much pressure I applied.  Click click click click....  I took the nozzle out and put it back in again.  Click click click click click click....  More pressure on the lever, click click click click....  Less pressure, click click click click....

At least for Sunoco this only happens at certain locations, and some worse than others.  I completely refuse to go to any Petro Canada these days because this problem happens to me at all their locations in the Land of Tim Hortons.

I lived in the U.S.A. for several years, and this only happened to me at one particular Shell station and at Sunoco a time or two.  In the Land of Tim Hortons I've found one Shell station where this problem never happens.  So I don't believe it's a problem caused by how I pump gas.  It's not rocket science.  At least, I hope not.