(Filename: Line: -1) Mass: 60019.3630699068 S: 202.816 MAC: 3.07232120978797 (Filename: C:/BuildAgent/work/d63dfc6385190b60/artifacts/StandalonePlayerGenerated/UnityEngineDebug.cpp Line: 49) NullReferenceException: Object reference not set to an instance of an object at ferram4.FAREditorGUI.CalculateStabilityDerivs (Double u0, Double q, Double M, Double alpha, Double beta, Double phi) [0x00000] in <filename unknown>:0 at ferram4.FAREditorGUI.StabilityDerivativeGUI (Boolean tmp) [0x00000] in <filename unknown>:0 at ferram4.FAREditorGUI.ActualGUI (Int32 windowID) [0x00000] in <filename unknown>:0 at UnityEngine.GUILayout+LayoutedWindow.DoWindow (Int32 windowID) [0x00000] in <filename unknown>:0 at UnityEngine.GUI.CallWindowDelegate (UnityEngine.WindowFunction func, Int32 id, UnityEngine.GUISkin _skin, Int32 forceRect, Single width, Single height, UnityEngine.GUIStyle style) [0x00000] in <filename unknown>:0 I encounter this problem when use Control Surface and calculate the stability. Also on action groups page,control surface cannot be selected.