On July 16, 2024, about 1430 central daylight time, a Piper PA-36-375 airplane, N2386X, was substantially damaged when it was involved in an accident near Avoca, Nebraska. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot reported that he maneuvered the airplane for his fourth spray pass and had rolled the airplane level at an altitude of about 300 ft above ground level when the airplane “lost all power” and began to descend. He added full power and pushed the propeller control full forward, but did not feel the engine respond and the airplane continued to descend. After he dumped the hopper tank load, he still was not able to stop the airplane’s descent. The airplane touched down in the field and continued through a cattle fence before coming to rest, resulting in substantial damage to the fuselage and left wing. The airplane was recovered to a secure facility for further examination. There was a crack observed between the Nos. 1, 2, and 3 cylinders; however, no thermal distress was found within the engine. Internal continuity was confirmed throughout the engine and borescope examination of the cylinders revealed no anomalies. Examination of the fuel divider, injectors, servo, and pump revealed no anomalies. The oil filter was removed and contained no contamination. The air inlet and filter were free of debris. While still attached to the engine, the left magneto flange could be rotated slightly. Both magnetos were removed and rotated by hand. The right magneto made a “clunking” sound when rotated and rattled when shaken. Both magnetos produced spark at their terminal leads. Further examination of the magnetos found the right magneto distributor gear was timed correctly. Both coil wedges were loose in the housing. The coil wedges appeared to have been initially wedged in place, but only had minimal marring, which may not have provided enough tension to retain the wedges properly. A review of maintenance records found that the magneto was overhauled on November 27, 2023, and was installed on the airplane on April 12, 2024. The airplane had flown about 40 hours since the magneto installation. The left magneto was in good condition and subsequently bench tested. The magneto operated as expected.