If your camera and lens were in my possession I would have 1. set the camera up on my Berlebach or zone 6 tripod and leveled the camera. 2. set up one of the test targets I have on 20 x 30 inch foam core parallel to the film plane. ISO 12233 , USAF 1951 , multiple 2 inch square copies at various angles in a + and X pattern, or the ones available at http://www.normankoren.com/Tutorials/MTF5.html 3. mounted a ground glass at the film plane and focused the old and new Biometers using an 8x loupe and comparing the results to the view screen using the loupe. I guarantee all readers that I would have found the focus error within the first hour and possibility had the view screen adjusted so that any lens attached to the body was in perfect focus at the film plane and view screen. If the body were warped from a drop a more serious focus problem would exist. Search engine Lens Test Target for full resolution versions and others, print them on a photo printer at its highest resolution. Glossy photo paper produces the sharpest image.