OK, I know the answer is to send it to Eric
which I may end up doing, but meanwhile I'll try to find if there's a simple solution to this.
In the camera mount, there's the aperture follower, it's like a ring that rotates around the mount, pushed by the aperture tab on the lens. This bit tells the meter circuit the aperture the lens is set to.
On my KX, the issue started as an occasional refusal to meter, fixed by remounting the lens. I also noted that closing down the lens had more resistance than opening it up. Actually this is how it still behaves - though recently when I moved the aperture follower by hand, I think I heard it squeaking.
Everything else on the camera works fine.
What's the fix?
thanks!