Do you have a data back on your camera. Last year My F4s had a very similar problem. After tinkering with it off and on for months, I took the data back off and put the regular back in its place. I decided to load a roll of film, its been working great since. I have yet to try the data back.
I have never owned a 6006 or 8008, is there a reson for staying with these models. I use a N-90s and N-80, if you watch the bay these models can be bought at a good price. If you want to spend a little more the F4 is hard to beat. Its built like a tank, so it is a little heavy to carry, to me its worth it. Also in a pinch it would make a good self defense weapon.
Hope I have helped, I am sure there others here that know more.