Can you post the serial numbers for the bad barrels you guys have? Might be able to see if they're all from the same batch other than BradAirs replacement?
Here's the high pressure line from my yh compressor. After isolating the tube as the leak I broke it to see the crack. The light color is fresh the dark area the leak. This was right at the top of the ferrule.
I've had leaks from the same place that randomly developed over time. I occasionally check all my fittings now between the heat and vibration things loosen.