On stop the Play Mode throw a error.
Probably it's happen because the DiplomataManager.Instance singleton is a property with a instantiate inside, and it is called on destroying some GameObject.

Reproduction recipe:

• Create a scene with script with a DiplomataCharacter component in any GameObject.
• Enter on play mode in the Unity Editor
• Exit the play mode

Log - version 2018.2.6f1:

Some objects were not cleaned up when closing the scene. (Did you spawn new GameObjects from OnDestroy?)
The following scene GameObjects were found:
[Diplomata]