I have a shapefile of 2' contours that I've converted into dwg format. I have an existing elevation field (double) in the shapefile that's populated with my elevation values. When it converts to dwg format there are some elevation values that don't carry over and populate as 0. These records all have an Entity field of Group instead of 3DPolyline. I've also tried the "Feature to 3D by Attribute" tool with the shapefile and it also assigns some of the contour lines to this Group entity and the elevation values don't carry over. There are approximately 50 of my 650 contour lines that don't carry over correctly. I've tried this with several shapefiles both in ArcGIS desktop 10.5 and ArcGIS Pro and the result is the same.
Why is this conversion dropping some of my elevation values and what can I do to correct this? Many of these dropped values are for a series of adjacent contour lines making it difficult to even extrapolate the missing values.