The fundamental problem is they tried to recreate a 1940’s design to meet 2010 certification standards. Everything was the gold plated over the top and over thought, like deciding that cabin doors had to have certified slides, which meant a huge amount of engineering and certification work to incorporate a system never envisioned for this class of aircraft
Also virtually every piece in was tested and tested until it failed some sort of inspection, and then since there are virtually no certified spares had to be manufactured from scratch at ridiculous cost. Everyone involved had never worked on anything that wasn’t factory new from Airbus and did not have a clue how to return a 75 year old big piston pounder to safe limited service.
They would have been far better to engage one of the well respected US restoration firms to do all the work. They would have spent much less and have an iconic flying aircraft......the whole thing is very sad.