Editing a prefab containing a VCam will log errors in the console.

1. Create a VCam in the scene
2. Drag the VCam object into the project view to create a prefab
3. From the hierarchy, click on the arrow icon on the right of the prefab instance to edit it
4. When in editing mode, select the VCam object and change some values in the inspector (just to make the prefab dirty)
5. Exit the prefab isolation mode by clicking on the left arrow on top of the hierarchy
6. A dialogue should pop up asking you to either save or discard changes done to the prefab
7. Click on either one

Result:
Error will get logged in the console about object being destroy and GUI related errors.
See console screenshot below.