ORD terrain model - Create from elements - Too many features for linking

ORD CONNECT 2020 Release 1 Update 8 10.08.00.88

I am trying to recreate an existing terrain model that we are currently using for a project. The current terrain was created by importing a .dtm file. The problem with the .dtm import is that all of the original .dtm features were assigned a feature style of Random Points. This creates an issue because we are receiving new survey that needs to be incorporated. We do not want to maintain a .dtm file and a terrain model. I have the original 3d base map file that coincides with the points from the .dtm.

I tried to create a new terrain model by using graphical filters. All elements imported fine. Panning around to compare the contours from the .dtm & the new terrain model I noticed some of the terrain model contours were inconsistent with the original contours. I realized that some of the triangulation was not correct. I updated the terrain from the graphical filter source data which fixed the contours associated with that filter (misc surface breaklines) but then other contours were wrong (roadway breaklines). Updating the roadway breakline graphical filter causes the misc surface breaklines to mis-triangulate.

I then started over by creating a new file from the project seed and merged the 3d base map into the file. Created an exterior boundary for the overall area using Create From Element. Then I tried using <Feature Management <Add Features. I turned off all levels in the file. I turned on my first level which is for sidewalks. I selected all of just over 8,000 elements. The import was successful. I turned the next level on which contained roadway edges and only has 3,200 elements. Everything was importing fine, but I received a message that states there are too many elements selected and could not be linked to the terrain. Do you want to continue with unlinked elements?

This is a big problem. I need the features linked to the terrain so that we can edit/remove/replace the elements in order to update the terrain model with the new survey.

I have been through this process several times trying to create features linked to a terrain. I continue to receive inconsistent results with importing elements. Sometimes I can import large amounts of elements without a problem then trying to a relatively small amounts of elements causes a problem.

How do I get around this problem?