I looked at the file you sent and was able to reproduce the problem. I found that there were a number of objects that had their visibility turned off. I deleted these and then tried again to save to a DWG file. It works now. Unfortunately this is the best work-around I have for now, unless you would be able to install and work with the 64-bit version of EnviroInsite. That for now would require you to have a 64-bit version of MS Office to be installed or no MS Office at all.
You may also want to explore the crop to rectangle option in the shapefile objects. That would reduce the items that are being drawn outside of your area of interest. One limitation in this option is that if one point of a particular shape is outside of the rectangle then the entire shape is not drawn.
