Complex sentence: The Lerwick was immediately found to be unstable aerodynamically and on the water and not suited to "hands off" flying, a major problem in an aircraft designed for long-range patrols.
Split into simpler sentences: The Lerwick was immediately found to be unstable both aerodynamically and on the water, and not suited to "hands off" flying. The latter was a major problem in an aircraft designed for long-range patrols.