This document summarizes an incident where a fast rescue craft experienced an unplanned descent from 23 meters above sea level while being retrieved. The descent continued even when controls were returned to neutral and the emergency stop was activated. An investigation found that both hoist brakes had functionally failed, likely due to the installation of an incorrect hydraulic valve. Four people were aboard but no injuries occurred. Key learnings included ensuring replacement parts are identical, understanding potential failure modes, following maintenance procedures, and ensuring third party maintenance tasks meet company standards.