Corridor Model - Active Terrain Keeps Deactivating (Reference)

Hi all,

On one of our projects in particular, we have a multitude of corridor model DGNs that reference the existing terrain model DGN. The terrain model DGN only contains one terrain and that is set to Active in that file. The terrain is also set to Active in the corridor model DGNs. We constantly have problems where the existing terrain has been "deactivated" in these corridor model DGNs. As you can imagine, this has become extremely frustrating, time-consuming to resolve, and is causing issues with downstream production and design. Has anyone else experienced this problem? 

Here are a few other key points, if it helps with a diagnosis:

• Project is in ORD 2021 R2 (10.10.21.4)
• Terrain model was initially built from an XML (multiple terrains were combined)
• Project is housed  on ProjectWise (10.0.3.453)
• We have tried detaching and reattaching the terrain model DGN, but this didn't help. 

Any help is greatly appreciated. Thanks!!