When the angle of the sun gets lower the shape of the shadows on the terrain appear to be unnatural. I would appreciate any suggestions greatly 
Is your terrain set to cast shadows? If not, it will look bad at steep angles. When the sun is high in the sky however, terrain shadow casting is a bit wasteful as terrain often won’t have very noticable cast shadows anyway.
I agree, double check that your landscape has “Cast Shadow” enabled, on it’s Details panel.
I would also suggest checking how your light source is handling shadow parameters. At Details > Light > Adavanced, you can play around with “Shadow Bias” and “Shadow Slope Bias”. Both start at 0.5 by default, test by increasing SSB to 1.5, the reducing SB to 0.3.
Additionally, if you are using VSM, you can adjust their resolution to improve the results. Use cmdlet r.Shadow.Virtual.ResolutionLodBiasDirectional and set it to -2.
Finally, from your screenshots, the weird shadows tend to cluster in certain areas. Try using the smooth sculpt tool in those areas, to improve how the terrain interacts with the lower sun.