Recipe(tried): Cooked Beans - A couple of suggestions

I have had same problem occasionally. would suggest either contacting Camellia Brand to order their (NOLA) kidney beans or you could start slower. I've recently only cooked my beans this way:

soak over night
in morning I rinse and add smoked ham hock and turn on very low flame for an hour or a bit more, add 2# smoked sausage, another hour, then add your veggies (onion, celery, bell pep, green onion, garlic, etc) and continue for another 2 hrs if necess.
I always go by the tenderness of the bean, but I do think when they don't soften it is because they are old, so try the longer lower flame at start before adding veggies.
Good luck!