Just trying to help the OP troubleshoot. His mash profile and all the rest points toward a very fermentable beer so I'm just trying to suss out why he would have gotten such poor attenuation.
I don't know either, but if he followed my recipe and process we can at least eliminate those as variables. Maybe thermometer miscalibration? Poor yeast health? Have no specific reason to suspect either...kinda thinking out loud.
The syrup alone would mean you'd have to really try to not get full attenuation.
To the OP: how was your starter? What are your Yeast management methods in general?
Thermometer was calibrated?
FYI, here's the recipe....http://www.candisyrup.com/uploads/6/0/3/5/6035776/dennys_400th_-_variation_002x.pdf