I had that happen on a Kimber Super America 308. It has less than 300 rounds through it and had never been stored with a compressed firing pin spring. The primers looked like they had been stuck just like the OP's, Nonetheless after checking firing pin protrusion and the loads I replaced the firing pin spring and it has been reliable ever since.
here is what I did with the input of some here on the fire. Clean out the bolt, check for any interference with the firing pin or spring with the bolt and if that doesn't work, either look for a softer primer brand or replace the spring.
