It could be a broken latch, but more than likely the underlug is the problem, it's not welded on the barrel plumb, I've had many H&Rs that showed uneven latch engagement, it can be corrected by honing the shelf, but I'd shoot it first and see how it does, if accuracy is real poor, it may have to go back to H&R for repair, see the repair page on the H&R website for more info it needed, their CS is second to none and will make it right, you can always ask them to cover return shipping as well so it doesn't cost you anything for the repair, just a little wait.
Tim