SerializedProperty fsm.variables.gameObjectVariables.Array.data[1].value has disappeared!
UnityEditor.EditorGUILayout:PropertyField (UnityEditor.SerializedProperty,UnityEngine.GUIContent,bool,UnityEngine.GUILayoutOption[])
HutongGames.PlayMakerEditor.FsmVariableEditor:DoValueField (UnityEngine.GUIContent,bool) (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Classes/FsmVariables/Editor/FsmVariableEditor.cs:106)
HutongGames.PlayMakerEditor.FsmVariable:DoValuePropertyField (UnityEngine.GUIContent,bool) (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmVariable.cs:459)
HutongGames.PlayMakerEditor.FsmVariable:DoValuePropertyField () (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmVariable.cs:470)
HutongGames.PlayMakerEditor.FsmVariable:DoVariableListGUI (System.Collections.Generic.List`1<HutongGames.PlayMakerEditor.FsmVariable>) (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmVariable.cs:443)
HutongGames.PlayMakerEditor.FsmControls:DoControlsGUI () (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmControls.cs:262)
HutongGames.PlayMakerEditor.FsmControls:OnGUI () (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmControls.cs:192)
HutongGames.PlayMakerEditor.FsmControlsPanel:OnGUI () (at C:/Projects/Playmaker_1.9.1/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmControlsPanel.cs:68)
HutongGames.PlayMakerEditor.PlayMakerControlsEditor:OnInspectorGUI () (at Assets/PlayMaker/Editor/PlayMakerControlsEditor.cs:52)
UnityEngine.GUIUtility:ProcessEvent (int,intptr,bool&)
It happens at runtime.
In my case, it was simply a string variable for the button tooltip that I exposed (input variable) so I could change it via the inspector.
I also use Playmaker Controller Component.
The problem disappears after you restart unity.
