I noticed that i sometimes get this error:
ArgumentNullException: Argument cannot be null.
Parameter name: key
System.Collections.Generic.Dictionary`2[System.Type,HutongGames.PlayMakerEditor.ObjectPropertyDrawer].TryGetValue (System.Type key, HutongGames.PlayMakerEditor.ObjectPropertyDrawer& value) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:588)
HutongGames.PlayMakerEditor.ObjectPropertyDrawers.GetObjectPropertyDrawer (System.Type objType)
HutongGames.PlayMakerEditor.FsmVariable.DoValueGUI (UnityEngine.GUIContent label, Boolean isAsset)
FsmComponentInspector.OnInspectorGUI () (at Assets/Packages/PlayMaker/Editor/FsmComponentInspector.cs:156)
UnityEditor.InspectorWindow.DrawEditors (Boolean isRepaintEvent, UnityEditor.Editor[] editors, Boolean eyeDropperDirty) (at C:/BuildAgent/work/d3d49558e4d408f4/Editor/Mono/Inspector/InspectorWindow.cs:850)
UnityEditor.DockArea:OnGUI()
Not sure if that could be related, we do have a couple of custom inspectors in the project.