The idea of an improved chamber has been mentioned. Could the dies been improved and not marked? If so you will be chasing your tail till you get correct dies.

Also on my 35 caliber sporter I had a similar problem mine turned out to to be an undersize chamber mostly near the rim. Factory cases could just barely chamber but cases that had been correctly resized would not. Chances of having an undersized original chamber are remote. Mine was cut with a defective reamer that the reamer manufacturer replaced.