I'd agree with Rob. Have the current shop replace the pivot ball, fork and bearing as it's a good opportunity while it's out of the car. But, explain to them first that you have discovered the problem and that all the work they did could have been avoided if they discovered the hydraulic issue first. If done tactfully, they may give you a really good deal on the above work, then back to crappy for the proper master to be installed and hopefully you're good to go.