I, too, had the same experience.  My advice for Buckfast aficionados is to
requeen every year!  And, that's sometime difficult because the 2nd
generation gals are difficult to requeen---they kill her even with a Thurber
long cage use.

My two hives are in densely populated downtown Seattle.  It doesn't work to
having the neighbors' small children stung by a mean bunch of 2nd or third
generation Buckfasts.  That's not mention yourself with dozens of stings
through your beesuit and veil!

The Buckfast queen is a prolific and efficient queen.  And the progeny are
industrious with great honey production.  But---requeen regularly!

W.C. Uhlman
Seattle