On my 39 - It was bought used from a shop I havecone to distrust,
which is no longer in business. It is one of only 2 Model 39's I have heard of with this problem, and I believe it was a broken part that the seller was trying to pass off....
I have owned other Marlins going back to the 1950's with NO problems at all, and they are the best choice in a lever gun, IMO.
I have had them in .30-30, .35, and .45-70.
I am another gun-carrying liberal veteran.