Unable to remove a burr

So I hollow grind my chisel, hone on 1k then 8k and go to remove the burr. I make a couple swipes in one direction but I think I can still feel a burr. The chisels have been flattened and I doubt my skills sharpening quite often. I flatten my stones every time I finish a blade. Is this a wear bevel that I am experiencing? Are my chisels somehow concave across the width of the blade?

i seem to feel the burr more in the center of the chisel

(.-.)

Unable to remove a burr