I would suspect your particular frizzen.
Most of my shooting is with a large Siler. My experience was that in the beginning I was not careful about positioning the flint and a dozen shots would ruin a flint. After I got more careful about making certain the flint struck the frizzen squarely, it worked beautifully, easily getting more than a hundred strikes per flint. These are almost exclusively English flints, bevel up, bevel down, whatever, and typically I don't begin dressing the edge until after perhaps 75 strikes. I have used deerskin, but most of the time I use scraps that are about 0.08" thick. None of it seems to matter. I usually snug down the jaws after the first 5-7 strikes. The Siler springs always seem $#*! for stout, but the flints bear up to it.