A lathe and some tools isn't that expensive. As a rough guess, that one is probably something like $20k worth of tools. Maybe double that including the cost of the floor space? Changing course and getting deliveries at sea is really expensive, so easy to imagine it'd pay for itself if you need it just once.
https://federatedtool.com/king-kc-1440ml-2-14-x-40-gearhead-... <- $7k for a quite capable lathe and some tooling.
Their engines were very unreliable, they could do overhauls mid-flight. Airplanes around that time were just as unreliable, but flew shorter hops. Had to overhaul or swap their engines quite regularly between flights.
https://www.facebook.com/PatriotsPoint.org/posts/the-difficu...
https://englishrussia.com/2014/10/26/sauna-in-the-submarine/