I had same issue last few weeks ago.
When I saw the image, some images showed too much vignet on some filters (Green and Blue).?
At first, I did not expect that filter wheel had a problem, but I found that those filters (green and blue) filters were not correct position.?
So I uncovered the front cover of camera and watched carefully, and I could see those filters were reallly not positioned correctly.
When filter wheel is rotated, O-ring is contacing with motor actuated shaft. When I see that, I could found that outter side of Oring is not perfectly rounding motion..
Maybe because of too much usage and rubber O-ring was changed a little...So I removed this Oring and disassembled again.?
and it works fine now...
