Is there a chance the threading just isn't lined up with the lower (I am thinking this would result in it still threading easily but the extension would be slight out of alignment for carrier travel.) It would mean a bad lower, but I am pretty certain every company glitches once in a while.
Other than that, the other two things I might consider are replacing the LPK components or testing these components in another lower. It doesn't sound like either is on the table right now, but without having it in my hands to compare with another unit that is about all I can think of.
