It even happens with the preview collapsed/hidden. It doesn't happen if I collapse the action itself.
Can now confirm it also happens with XML Get Node Properties, using the combination as shown in the attached images. The first image is the action when it is displaying properly and the second shows how the action and the editor looks when it glitches.
Here are the main errors that spam the console during the glitching:
ArgumentException: Getting control 1's position in a group with only 1 controls when doing Repaint
Aborting
UnityEngine.GUILayoutGroup.GetNext () (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:665)
UnityEngine.GUILayoutUtility.DoGetRect (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:372)
UnityEngine.GUILayoutUtility.GetRect (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:332)
UnityEditor.EditorGUILayout.LabelField (UnityEngine.GUIContent label, UnityEngine.GUIContent label2, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:5437)
UnityEditor.EditorGUILayout.HelpBox (System.String message, MessageType type) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:6833)
HutongGames.PlayMakerEditor.StateInspector.DoActionsListGUI (HutongGames.PlayMaker.FsmState state) (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:451)
HutongGames.PlayMakerEditor.StateInspector.DoActionsPanel () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:327)
HutongGames.PlayMakerEditor.StateInspector.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:200)
HutongGames.PlayMakerEditor.InspectorPanel.OnGUI (Rect area) (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/InspectorPanel.cs:164)
HutongGames.PlayMakerEditor.FsmEditor.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmEditor.cs:539)
HutongGames.PlayMakerEditor.FsmEditorWindow.DoGUI () (at Assets/PlayMaker/Editor/FsmEditorWindow.cs:95)
HutongGames.PlayMakerEditor.BaseEditorWindow.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/BaseEditorWindow.cs:72)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
ArgumentException: GUILayout: Mismatched LayoutGroup.Repaint
UnityEngine.GUILayoutUtility.BeginLayoutGroup (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options, System.Type layoutType) (at C:/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:273)
UnityEditor.EditorGUILayout.BeginHorizontal (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:6970)
UnityEditor.EditorGUILayout.BeginHorizontal (UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:6949)
UnityEditor.EditorGUILayout.LabelField (UnityEngine.GUIContent label, UnityEngine.GUIContent label2, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:5435)
UnityEditor.EditorGUILayout.HelpBox (System.String message, MessageType type) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:6833)
HutongGames.PlayMakerEditor.StateInspector.DoActionsListGUI (HutongGames.PlayMaker.FsmState state) (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:451)
HutongGames.PlayMakerEditor.StateInspector.DoActionsPanel () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:327)
HutongGames.PlayMakerEditor.StateInspector.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/StateInspector.cs:200)
HutongGames.PlayMakerEditor.InspectorPanel.OnGUI (Rect area) (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/InspectorPanel.cs:164)
HutongGames.PlayMakerEditor.FsmEditor.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/FsmEditor.cs:539)
HutongGames.PlayMakerEditor.FsmEditorWindow.DoGUI () (at Assets/PlayMaker/Editor/FsmEditorWindow.cs:95)
HutongGames.PlayMakerEditor.BaseEditorWindow.OnGUI () (at c:/Users/Alex/Documents/Unity/Playmaker/Projects/Playmaker.source.unity/Assets/PlayMaker/Editor/Classes/BaseEditorWindow.cs:72)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)