On older torpedoe models and early Mark versions, the hydrostatic valve was located in the middle section of the weapon, just behind the warhead. To increase range and speed, this space eventually became filled with additional parts and fuel. As a result, the valve was moved farther aft. This revised layout was originally perceived as a benefit because the depth control mechanism would be closer to the rudders it controlled. Its final location was the tapered section of the torpedo near the tail. No one realized that by placing the valve at a slight angle to the weapon's longitudinal axis, it would cause a corresponding change in how the valve reacted in determining depth control. This variance was minimal under what were considered to be normal testing conditions–shallow depths, weak currents and calm seas.

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Further complicating the problem, it was later found that the depth-recording instrument used by the bureau to check the reliability of all hydrostatic valves was miscalibrated. Years later, technicians discovered that the recording instrument and the misplaced valves erred in the same direction and amount. The bureau had been cursed with pure bad luck. Two completely different devices, each responsible for checking the other, deviated identically for vastly different reasons. This unfortunate coincidence explains the bureau's initial testing results and its rejection of Lockwood's evidence. It was a very peculiar and costly twist of fate.

Adding insult to injury, earlier improvements by Commander King, although well-intentioned and initially successful, added to the depth-control riddle. When the additional 115 pounds of TNT were squeezed into the Mark XIV warhead, the exercise heads were not correspondingly altered to reflect the change. The extra explosive had been packed into the warhead by increasing density, so although the water-filled exercise head continued to occupy the same space as the warhead, it no longer had the same weight. Thus, the Bureau of Ordnance was using one version of the Mark XIV for testing and issuing quite a different Mark XIV.

The problem of designing identical torpedo heads was solved by using Lockwood's calcium chloride solution, which correctly matched the warhead in size and density. The hydrostatic valve problem was alleviated when a new, calibrated depth-control valve was designed and installed on all Mark XIV torpedoes. Once these improvements brought the Mark XIV up to the correct depth, however, the Mark VI magnetic detonator presented additional problems. The "Silent Service" was no closer to having a reliable torpedo than it had been eight months earlier.

During World War I, the Germans had developed a mine with a magnetic detonator. With continued improvement, it became a very effective weapon in World War II. The key to the secret detonator was a compass needle that moved when acted upon by the hull of a steel or iron vessel. When the magnetic needle swung, it activated an electrical contact that exploded the mine. Between the wars, every major navy attempted to duplicate the magnetic exploder in its standard submarine torpedoes. Conventional theory held that if a torpedo could be exploded under a ship, as opposed to alongside, the damage would be much greater. Ideally, one or two torpedoes detonated directly under a vessel would be enough to break the ship in half.

By 1925, the Bureau of Ordnance had completed a basic magnetic detonator. Unlike its distant German cousin, the American model was not activated by a compass. Instead, the bureau used induction coils that generated an electromotive force, which changed when the torpedo passed through or under a target's magnetic field. Vacuum tubes magnified the change within the coils to release the firing pin. The design was extremely complex for its day, but that complexity compromised the detonator's reliability–as did the secrecy imposed by the bureau.

The bureau felt that the Mark VI magnetic detonator constituted a secret weapon by the late 1930s. The detonator was cloistered from all but a select few until the spring of 1941, when war seemed imminent. The bureau feared that knowledge of its existence would influence the design and construction of a potential enemy's fleet, primarily Japan's. In April 1941, Mark XIV torpedoes with Mark VI detonators were finally issued to the fleet, although security restrictions continued. Only commanding officers and torpedo officers were allowed access to the secret weapon and its manual. Common sense, however, dictated that enlisted torpedomen should also be allowed access, because they were expected to maintain and service the ordnance. Yet when war struck seven short months later, few if any men in the Pacific theater understood the inner workings of the detonator, and since only a few knew what a Mark VI would do under perfect working conditions, even fewer could recognize a malfunction. As with the Mark XIV torpedo's depth mechanism, it would take the rigors and sacrifices of combat to expose the detonator's fatal defects.

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