cr17,
Of course, Rottweil and Dynamit Nobel are known brands, most often seen in ammunition. I recall having seen them on guns and telescopes as "house brands" manufactured by someone else. I really don't know about the specific guns but some guns that have a selector on the side are made with only one lock, used with both barrels, depending on the location of the selector. If one barrel is fired and the selector is moved to fire the other barrel, it won't fire unless the gun is re-cocked. This is not really a malfunction, but a design feature. I have no idea if this is your problem or not but is something to check.
Mike
