vonBaloney, I think you are on to something with the contacts. I just tried what you eluded to with both my K5 and K10. The K10 will indeed attempt to close the aperture with no lens attached, while the K5 will not. The two manual lenses I have that work both have shiny silver mounts, while the lens that will not work, has a black mount. A quick check with Ohm meter shows the working lenses conduct quite nicely, while the non working lens is a poor conductor.
Awesome observation, not sure if the issues can be fixed but I can quit pulling my hair out.