Why am I getting the error " Failed to create device file: 20 The process cannot access the file because it is being used by another process."?

I made a simple Unity3D game:

I imported the Kinect for Unity plugin included with Kinect SDK v2.
I added a 3D model.
I created a script that opens the Kinect and tries to read a body frame.
The Kinect starts fine.
Yet every time I try to run this line:
BodyFrame frame = frameReference.BodyFrameReference.AcquireFrame()
I am returned a NULL pointer, and I see the below in the Console on Unity3D:
Failed to create device file:
20 The process cannot access the file because it is being used by another process.

What am I doing wrong?

Figured it out:
I had to implement OnApplicationQuit() method and do proper Kinect clean up within it to avoid this.