1. Load/Create a new scenario in 3DEN (you can just place a single unit)
2. Run the mission.
3. End the mission and go back to 3DEN. Notice that the entity list is completely empty (even the categories are gone)
4. You can try reloading the mission (Scenario > Open), but it won't solve the issue
5. Click on the "Expand all" button. The entities will appear now