I think I've figured it out.  From my testing, it looks like it is the size of the polygons that is causing the problem.  My curved wall is 32 poser feet across and 10 feet tall.  The wall is broken up into 320 faces, each approx. 1.57 poser feet wide by 2 feet tall.  I first tried triangulating the faces to see if that would help, but it didn't (but it did look cool).  I then went back and smoothed the wall which subdivided each face into 4 faces, but I still had the problem. So I tried subdividing again, and it appears to have worked.

I'm attaching the triangulated original wall to this post and I'll attach the 2x smoothed one to the next post.