OK, I've reduced the transparency and featering (blurring) until it's almost unnoticible. Other than this I can't follow HD's points.
... a real shadow would track with the light source and POV
There is only a single POV and as it's only a 25 second animation so what's to track other than below the train. I realise the other items in the animation have no shadowing but for this purpose it suffices. If you wanted to go into HD's accuracy you'd need to use a 3D program like Cinema3D or Blender.

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