It would be an easy problem to solve if its just improper fit. I have a problem where I have a lump bone chip at my right heel thats not outright visible and hard to measure/trace; it clearly there on x-rays. I have a pair of boots that sometimes aggravate the lump after a few hours of walking and I sometimes get blisters. I am suspecting a poor patterning/skiving job, but will play around with knocking the heel stiffener softer. It's most probably celastic.