1. Who made the malfunctioning magazines? Taurus? Triple K? Some other maker?
2. If the new magazines are pushed past the release and all the way in, when you press the release again do they fall out of their own weight? Or do you have to pull them out?
3. When the new magazines are pushed all the way in, and you fire the pistol, do they feed cartridges correctly? Or do they cause occasional jams?
Finally, is it possible that there are two different models or iterations of your PT738 pistol, and the new magazines are for the other iteration?