#24. "RE: How'd I screw up? Exposures off as zoom in" In response to In response to 23
The contrast of the scene is unlikely to be having an effect. If you mean "low light" rather than low contrast, then this does point towards an aperture stop-down problem, as in low light a wider aperture would tend to be selected.
It must be frustrating to have the equipment come back with the same fault, but it's always useful to carry out as many tests as possible to try to isolate the problem. It really would help to do a brief further test as I described above.