I have a problem with my Marlin 795's last shot bolt hold open?

I took my 795 to the range for the first time today. The LSBHO worked after the very first mag. Then after that, it stopped holding open. The first batch of ammo we shot was really old and dirty POS Remington ammo (really really old, really really dirty). Then the second batch after that was new, never-been-opened Remington .22 target ammo. The first mag of that held the bolt open, but that was it, never again after that. The Remingtons were very bad. There was one dud and they stopped ejecting manually after a while, but would cycle properly when fired. Then I moved on to CCI mini-mags, and even THAT wouldn't hold it open. I ended up dry-firing the rifle a lot today, and I would cringe every time I heard that "click", in fear of having broken the gun. As much as I would hate to do it, I'm thinking about returning this rifle and getting a Marlin Model 60, or maybe a Marlin 925.