If you take off your primer feed and look at the "bearing" plate, see of there aren't minute scratches in it. I encountered the same thing after many thousands of rounds... I've used all types of lubricants, from dry graphite to white lithium and not one solved the problem... Until I contacted Dillon and they sent me a new bearing plate.
Then again, check out this thread:
http://www.brianenos.com/forums/inde...owtopic=181925 It goes a LONG way to explain the whys and hows of this happens. You ain't the first, and heaven knows, won't be the last!
If I recall correctly, Dillon uses a Teflon coating on their primer plate.