The shoulders have grown (most likely) or the case head spacing is long. Full length size your brass and check the brass length to ensure they are not long. Old school thought used to be that neck sizing was more accurate, but not so as the chamber is not 100% round and headspace issues like what you experience cause the case to be misaligned.
Don't try to can the bolt over on these cases as you run the risk of falling the bolt lugs, an expensive problem.
