Since the OP wrote to us before this thread was opened, and apparently didn't accept our answer, I would like to publish it here:
We examined the retention sample from the production lot in question.
When checking the diameter of the slugs, we get values between 5.50 and 5.508 mm, which corresponds to .2165 to .2169 inches. So the slugs are minimally undersized, but within an acceptable tolerance.
We use calibrated micrometers for measuring, and check all production lots several times during production and before packing. So it is virtually impossible to get heavily undersized (or oversized) slugs.
Best regards
Jƶrg