To reproduce:
1. Open attached project
2. Select banner1 object
3. Add cloth component
4. Notice errors in console:

get_skinIndex is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'ClothInspector' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEditor.ClothInspector:.cctor()

LoadAssetAtPath is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'ClothInspector' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEditor.ClothInspector:.cctor()

UnityException: LoadAssetAtPath is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'ClothInspector' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.

The targets array should not be used inside OnSceneGUI or OnPreviewGUI. Use the single target property instead.
UnityEditor.DockArea:OnGUI()

Before 5.4.0b9 this error was printed:
GetLocalizedString is not allowed to be called from a MonoBehaviour constructor, call it in Awake or Start instead. Called from script 'ClothInspector' on game object ''.
See "Script Serialization" page in the Unity Manual for further details.
UnityEditor.ClothInspector:.cctor()

Regression from 5.3