I will test my scales with a measured volume of water. I will have to measure the fermenter with 1L jugs, though it will allow for cumulative error.
I am starting to think that this has to do with buying pre milled grain. when you shake a bag of pre milled grain, you will see the hulls rise to the top and the endosperm fall to the bottom. My bags may have more endosperm than hull, I'm assuming that the endosperm is the starchy bit.