I got this error from Unity (2018.3.3f1) while I was working with a large script and changing data that was serialized into a scene.
“Unsupported type Vector” was the error but it had no call stack and no explanation of where it came from.
The solution was to delete the component from the scene, save the scene and then re-open it and re-add the component. Sounds weird but I have verified that it solves the problem.
This is all that was shown in the output window: –