Are all head stamps the same ? Are all case lengths the same? Are all crimps the same? Had a similar problem years ago with a 32-20. Had mixed headstamps, about 5 different ones. All "cartridge" OAL's were correct, but because of the different headstamps they were crimped in different places. I found out that each brand had a different "case" length. Trimmed them all to the shortest case length ,,, no more problems. Just something to check.
Good luck