Magpul posted that there are some problems with some of their Glock magazines. It happened due to a critical geometry changes that did not make it into the initial production molds.
The corrected version will be available around May 4th, and date coded 5/15 or later.
-If you purchased your magazines direct from Magpul, Brownells or Midway, you do not need to do anything, replacement magazine bodies for the magazines ordered (1 for 1) will be shipped to you automatically.
-If you purchased your magazines from a gun store, replacement bodies will be sent out to the store in question for you to pick up.
-If neither of the above works for you then Magpul customer service will handle the replacement directly.