Yeah, looks like a pretty fermentable grist overall. Any problems with temp control this time? Flocculant English strains are prone to stalling if temp goes down during fermentation and benefit from raising temp after a few days to attenuate properly. Did you pitch the same amount of yeast as usual, I assume? Did you use a refractometer to measure FG? If so, there's a correction you need to use to get an accurate reading. Correct the reading for temp? Also, a 1.066 beer, while not huge, will generally finish higher than a 1.050 beer as well.
Finally, software estimates of attenuation and FG are utterly worthless. Your FG (and attenuation) depends on lots of factors - grist, mash temp, pH control, yeast health and quantity, etc. Though most of your beers finish ~ 1.012, lots of yeast/grist/mash temp combos will make beers that don't.