Did they run a bleed of nitrogen through the lines WHILE brazing?
Not to pick on you, but when you buy your own equipment you are taking money out of the contractor's pocket. Many guys won't touch it. And you do realize you have no labor warranty if the equipment fails within its warranty...5 to 10 years!
Of course he should warrant his install ( tail light warranty?). Hard to evaluate the photos. Might be time to have a heart-to-heart sit down with him. Possibly offer him some more $$$ to come over and check things, make it right as necessary.
What brand did you get? Buying on line is always a crapshoot.