Hi, recently got my yashica electro 35 GS serviced for POD problem. Now the shutter mechanism works fine (i tested under different apertures and it opens and closes without any problem) and the light meter works fine. But when i shot a film (400 ASA; shot mostly indoors near window with plenty of light) and developed it, found that it is underexposing by as much as 2 stops. Any idea what could be the reason and how to repair it? Thanks for any suggestions.