Contax 159 &167mt lens aperture failure?

Hi there. am looking for a little advice regarding a Contax 159 I bought recently and my Contax 167mt, when fitting my Contax 28 mm and 50 mm lens's to the cameras the aperture reading in the cameras viewfinders does not correspond with that set on the lens's. However when I attach the same lens's to two Yashica FR's I have the lens aperture settings does correspond with the aperture readings in the camera viewfinder. I can only assume that there must be some failure, electrical or otherwise with the Contax camera bodies. Any advice would be greatly welcome.

Thanks

Nigel Sinkins