78 Corvette brake conundrum...

Who did the master come from?
I had a couple parts store units a few years ago that wouldn't push fluid. Brand new, right off the shelf, something was up with the piston bypassing fluid. Sucked!
Right now this is the best that I can think of is well that he just got a bad overseas part... Like I told him autoshop 101 just because it's new doesn't mean it's going to work..