OK--the right batteries are important, but in this case of all batteries being new, alkalines lose their power in a constant downhill slope from their new condition, resulting in more and more overexposure, but in subtle amounts. What you have here is clear. You have one or both meter cells bad. If you experiment, you will see that you may be 2 stops off at one light level, 1 stop off at another, and close to accurate at still another. Classic symptoms of a bad cell. I believe the FE used silicon cells, and the meter circuit is somewhat akin to a low signal audio amplifier. At 2 stops off, I do not believe I have ever been able to adjust out the problem, and it certainly cannot be adjusted out for a flat response from dark to light. Bad silicon cells, one or both.