If you have a Contax RTS II, can you check something for me?

I went to a camera fair this past weekend, and bought a nice looking Contax RTS II. I thought I'd checked that all functions were correct, but it seems I overlooked one: I didn't verify that the f/stop indicated in the viewfinder display matched what was actually set on the lens. Now, several days later, I see that there's a variance, one that seems to increase as I move from a 50mm to a 28mm lens. In other word, I'll have the camera set at f/11 and the electronics think I've got it set to f/6.3.

In the Contax lens mount on the camera, there's a rotating tab that, with no lens attached, stands at about the 2 o'clock position. That's the tab/ring that reads movement change when you change f/stop. And just above the foam strip where the up-swinging mirror hits, there's a small tab that moves in a horizontal movement. This tab is engaged by a prong on the back of the Contax lens when it is mounted, and it's this tab that let's the camera know what the lens' maximum aperture is. Between this small horizontal-movement tab giving the maximum f/stop and the rotating ring that inputs f/stop movement, the electronics know what f/stop to indicate.

So here's what I'm curious to know, if you have an RTS II. If you remove your lens and point the body at a relatively bright surface and push the exposure check button, what f/stop number do you see? I bet that you see f/1.2 -- that's what I see in my RTS II, and that's what I see in my 167MT. But I want to check versus another RTS II.

And if you reach in and push that small tab above the mirror to the other side of its slot, what do you read? I think you'll get f/4.5.

If I'm right, if everyone else gets 1.2 and 4.5, then perhaps the fault lies with the electronics. I can correct for the error with the +/- exposure control, but with a 28mm lens the error is approaching 1 2/3 stops when you get toward f/16.

Thanks to anyone who can check their RTS II, and if anyone else has had this problem -- how did you fix it?