This bug was originally reported on the #pyshotgun-facebook channel.

Basically the state of DragAndDrop is not properly reset after a Drag originating from Unity. If you would drag from another application unity AFTER a drag from Unity the objectReferences array is never cleanup. See video for repro clearer repro steps. This only happens on Windows.

0- Ensure you have a cube in your scene
1- Drag a material to an external application (ex: Visual Studio Code). This sets the objectreferences of the DragAndDrop class.
2- From the external app, drag any file (not the same you previously dragged) onto the cube
3- See that the material is assigned to the cube