Do-it has a jig mold there at HQ with 1 million plus castings; I still have Dad's first mold (still working) from the early 70s. It's most likely debris as mentioned above, but if not...
I noticed a similar problem with the poison tail mold since the hooks have been made in China vice Norway. The bend on the hooks is no longer as tight and pushes against the weed guard pin; without bending the hooks a little extra yourself, you don't get a good fit between the two and it results in fairly consistent flashing. My point is even though all hook and swivel "numbers" may be the correct ones, a switch in manufacturer facilities could have things just a teeny bit off and you are getting flashing as a result of that.