Hmm. With respect to the back, what is "the simpler 12 version"? The one you show in the photos is a pre-A12 model, in other words it doesn't have the "automatic" mechanism that sets the first frame position just by turning a crank on the right side. Far as I'm aware, that's the "simplest" 12 exposure magazine for a Hasselblad 500 series camera.
Yes, the aperture reset problem has to be in the lens. It may work in just by being exercised, but the lens should probably should be given a CLA.
So you have a relatively modern body, a relatively ancient back, and a lens from likely somewhere in the middle.
(You can find the dates the lens, back, and body were made using the lookup mechanism on the
Hasselblad Historical site ... )
My 500CMs were both produced about 1978-1979, my SWC/M about 1976.
G