I have watched each video several times and I see no "shaking uncontrollably". Do you mean the "wavering" shadow effect on the signal post in the last video?
I have just looked at the shadows of stationary and moving objects in my own sessions while I rotate the camera point of view around them and I can see no such effect. It could be your Shadow Quality Setting in the Performance tab of the Trainz Settings. Try adjusting that to see if it makes a difference.