I have owned an SDB since the early 90's and have loaded countless thousands of 45 ACP and 9mm rounds both lead and FMJ.

Recently, I have noticed that I am getting between 5-10% of the reloads that do not fit correctly in the case guage.  After I finish, I take out the brass pin that coincides with the seating die, place the rounds, reseat, and re-crimp.  This usually cures the problem, although I have had to go back and repeat the process multiple times. 

This problem while not huge is annoying because I find myself running each and every round through the case guage to segregate the good rounds from the bad.  While I am able to load between 300 and 400 rounds an hour, it takes me much longer to check each round.  I used to only check about every 10th round or so with no hiccups. 

What could be my problem?