I recently trued-up my wheel (done several times before) and then used the grading stone to go down to 1000 grit. While grading the stone, I noticed that there was a small section of the stone that had a clear drag and a sound as it passed under the grading stone and I cold feel it with my fingers.
I sharpened a few knives, but it was nothing like I have had in the past.
Does anyone have any thoughts or recommendations?
Probably not the answer you're looking for, but try truing the wheel again. These inconsistencies in the stone composition are usually only a few thousandths of an inch thick.