soft brakes and brake light comes on-help[

I would suspect the remanufactured master cylinder is leaking fluid past one of the cups not allowing front or rear circuit to full pressure. I have had terrible luck with remanufactured hydraulic brake parts over the years including the ones I did my self.
Where these cars have readily available new manufacture master cylinders, and wheel cylinders for a few bucks more than rebuilt why would anyone not get the new stuff?