Look and see if the line from the reservoir goes to the pilot side pedals. Most go to the passenger side first. Going to the pilot side first, and having an air bubble in the line to the passenger side will make the pilot side fail and not the passenger side.
Bleed from the bottom up to clear the air.
Keep in mind, if the reservoir line is going to the pilot side first, your brake system now has many more points of failure. And you can't apply the brakes if the passenger has any pressure on the brakes....... you are pressing through the passenger cylinders and they must be open in the full released position.
Next time you replace the brake pads, just push the piston back in flush and install the new pads. Check res. level done.