You introduced too many variables (different brass, primers, powder) into the equation to solve the problem. Eliminate some of the variables and try again.

You could have some pieces of the Win brass that were sized too short. Win brass ain't what it used to be.

If you have a set of head & shoulders gauges and a caliper, you could measure the shoulders of the fresh fired cases and compare them to those that didn't fire. My guess is that the shoulders are pushed too far back.

Could also have some bad primers.