Renderer.PickProp does not work when SSAO render-pass is set
The PickProp function of renderer does not work when a SSAO pass is present.
This is easily worked around by setting the render passes to None before executing the PickProp function:
store = renderer.GetPass()
renderer.SetPass(None)
assemblyPath = renderer.PickProp(self.start_x, self.start_y, self.end_x, self.end_y)
renderer.SetPass(store)
But it makes more sense to add this the the PickProp function itself.