Art,
I have the same problem with the two I checked as we did in the past. I can't get the knob on far enough for the locking pin to engage and hold it on. PM me your info so I can get you a refund. You can then use the part or throw it away. I don't need it back.
As a general plea, I would ask if you have a problem with one of our parts that you email us, email me or call us so we can act on it. Even if you are resourceful and make it work, like many of us LBC owners are. Please alert us if you can.
Thanks,
Shawn