I did not read all this thread and in a harry and I do not know if is this case but:
Rhino freeze when dragging or copy and paste and instantly using gumball move or copy. I remember experimenting with this problem when a shader material with a big texture is applied to it. Somehow was reported into a bug. What I was able to understand is that some people use big BMP or Tiff texture files (big in Mb instead of jpg) and Rhino bug is physically copy when them when moving the object or similar issue. this is hypothetical because I do not remember well.
To fix this I take out the material and the texture. I apply a 512x512 png texture.
Probably reported here:
https://mcneel.myjetbrains.com/youtrack/issue/RH-47093
And some light at the end of this thread: