AI coupling tab ring sticking

[BAphotos]

My D300 is having a problem with the AI coupling tab ring sticking. When I use lenses with the AI coupling, if I have the aperture closed down, then open it up the ring will move very slowly. In some cases it moves well, others not, just random. I'm wondering if it's just dirty (it's been through a lot of desert environments, and sand/dust is visible in that area), if so I'm wondering if anyone knows how to clean it? Any other ideas would be greatly appreciated.

 

[Derrel]

Thin piece of strong, quality paper or thin,stiff vinyl or plastic.

 

[BAphotos]

Thanks for the tip! It's working better already. I've got to go through and do a real heavy cleaning one of these days soon.