The US Coast Guard recently launched the "first article" of a new generation of coastal patrol ships, designed by a low-bid outside contractor with minimized oversight and control by USCG personnel in order to lower project costs. One of the intended design features is a modular "power pack" for the ship's engines and closely related equipment, intended to be able to be hoisted vertically into and out of the ship's lowermost hull extent at overhaul time and quickly replaced with a second power pack so that overhaul time can be minimized and therefore the ship's duty-availability days/year can be maximized. This hoisting is to occur through a hoistway that is cleared by temporarily unbolting and lifting out modular sections of the ship's internal structure and upper-hull functional equipment.
Ships are built with internal "frames", lateral structural elements sort of like human ribs that reinforce the hull. These are spaced every 25 feet or so in this case. Ships' internal design features are always considered in regard to which frames will structurally support them, and between which they must fit.
My understanding is that one team of outside contractor engineers was responsible for design and functionality of upper-amidships hull functionality and structures, and another team the corresponding lower-amidships functionality and structures. Due to a design/document control mistake, the powerpack location and corresponding lower-hull hoistway were mis-aligned with the upper-hull hoistway by one frame...and this wasn't discovered until the ship costs were essentially 100% committed, with subcontractor elements of the ship already built, delivered to the final assembly shipyard, and partly assembled.
For cost reasons they built the first ship anyway. My understanding is that the revised intent is that when the time comes for the first powerpack maintenance cycle, they will tear the ship apart and rebuild it per a revised design yet to be created that will make engine access possible.