Good info above.
Sometimes,, it can be crimped primers.
Sometimes you can get Berdan primed cases,, but as noted, not too often.
Another thing.
A good friend, (and lurker here,) recently experienced the same thing. Apparently he has broken pins & bent a few rods. He called RCBS,, and found that there is an "extra small" diameter pin to be used in some brass. He bought some spare rods & a bunch of pins, (off Midway.) RCBS also replaced some of his broken stuff.
You may have some brass with the extra small flash hole.