Sonata won't start after getting gas

Recently my wife's 2011 Sonata has been having a lot of issues starting
immediately after fueling, and ONLY immediately after fueling.  The brake
pedal becomes very hard to depress, and the engine sputters several times.  
Eventually it will start up, but it's annoying.  We took it to a mechanic and
had the purge valve solenoid replaced, and now the issue is actually worse.  
We brought it to our local Hyundai dealer but they were unable to diagnose
any problems.

I've read a lot about the purge valve solenoid being a known issue on this
car, but could there be another cause?  The garage looked at the solenoid to
ensure it wasn't faulty and they claim it is a good part,

Any help would be MUCH appreciated!