Shadow Animation Glitch?

[coenrw]

Modeling a 2.7 MW array in 3D, I'm finding odd behavior when using the Shadow Animation function in the Global scene view.

 

 

The bottom four rows shown above is a single Collector field in sheds partitioned into module chains 2.0 in height. The shade objects are identical octagonal prisms representing utility poles. As can be seen, the two shade objects to the left are having a full electrical effect on the strings (chains) they shade. The two on the right appear to have no electrical effect on the array at all. Is this simply a graphical glitch or does it indicate a deeper model calculation error?