Common issue with the banjo bolt, thin washer is one concern. I often reuse the old ones. Annealing works.
Make sure the sealing surface is clean, a piece of grit csn cause a leak too. I tighten/loosen bolt two or three times going a little tighter each time, and i often use a wrench. It is imperative there is zero fluid leaks.
also with those calipers, notches on pistons must align with pins on brake pads, and cycle e-brake to wind piston out to take up slack between rotor and pads. Failing to do this will result in a low pedal. I have serviced quite a few of theses types of brakes.