If it was either the viewfinder screen or eyepiece diopter, would not all lens attached have a focus problem?
You're absolutely right and I apologize for that omission. I imagined I mentioned that after I got distracted by something else. Sure, if you can duplicate the problem from one lens to another then chances are it ain't the lens. Thanks for noting that. Sometimes it could be that the focusing screen itself isn't really the best match for the lens although I've made do with a lot of different F2 focusing screens.
Without guys like John Coltrane, Count Basie and Duke Ellington, life....would be meaningless.