Development became protracted due to the E15K1's advanced features, and the project fell behind schedule. Problems were encountered with the retractable stabilizing floats, resulting in several accidents when the floats could not be lowered for landing, and the system was eventually abandoned, with the stabilizing floats being fixed, and a more powerful Mitsubishi MK4S Kasei 24 engine fitted to compensate for the increased drag.
Development was delayed due to the E15K1's complex features, and the project suffered from a scheduling setback. Issues with the retractable stabilizing floats caused several crashes when they could not be lowered for landing, leading to the abandonment of the system. Instead, modifications were made to the stabilizing floats, and a more powerful Mitsubishi MK4S Kasei 24 engine was fitted to mitigate the increased drag.