MZ-S question

The MZ-S records the exposure mode, metering method, shutter speed, aperture and exposure compensation on the negative outside the actual photo area, but on mine the result is always a couple of overexposed smudges while I use ISO 125 or 400 films and I have played with the programmable settings on different films to play with the intensity but the results are the same.
Do you have an idea of what the problem could be?