I agree it doesn’t sound at all like your dogs, but have to disagree some on the dogs not eating what they kill point. My Uncles two German Shepard’s will kill and eat cats, Raccoons, Rabbits, and Squirrels (all of which have been seen being consumed by them, and no, they aren’t underfed).
I like the hasp and carabiner lock best myself, but also use sliding bolts in places. Because I use Chicken Tractors on uneaven ground the bolts are often incredibly hard to operate (even for me).
So sorry for your losses

really though IMO the most important thing you can do to prevent predation is get everyone in and locked up at night, it sounds like making that change will solve most of your problems.