Actually, this is by design. To be safe, the shotgun needs to have the hammers cocked before one can insert cartridges, else a gun could be fired and opened partially, new cartridges inserted and closed without cocking the hammers, and could fire when closed. Kind of the same issue with an ejector gun; the hammers should cock before the ejectors trip. A lot of new guns are fitted so tightly it is not an issue till they wear in. Well fitted guns generally cock just before the barrels can be unloaded or loaded, but some require a lot of effort to over cock to be able to load or unload. And sometimes someone working on trigger pulls can shorten the sear noses which exacerbates the over travel issue.
