Why Mark 15 torpedoes were improving by late 1943

Were American destroyers still suffering the same torpedo problems at this battle?

Many Mark 15 faults had been corrected by late 1943, especially in commands with active testing and technical support, though the fixes were only just becoming complete.

The Mark 15 shared parts of the Mark 14 torpedo's difficult history, including material and detonator problems. Early Mark 15 manufacture used zinc instead of cadmium for internal plating. Destroyer crews could conduct more practice firing and testing than submarine crews, giving them additional opportunities to expose faults. Weapons were improving from mid-1943, although the corrections were not fully complete until November. The Seventh Fleet intervention involved disabling magnetic detonators and fixing contact pins, while corrections reached the South Pacific command more quickly. Proactive commanders such as Merrill, Burke, and Austin helped turn technical lessons into working weapons.