When trying to reopen a level with landscape under mobile preview, landscape's render data is not generated correctly.
1. Create a new level in Editor.
2. Create landscape in level and save the level.
3. Change "Preview Rendering Level" to "High-End Mobile"-> "Default High-End Mobile"
4. Reopen the level in content browser.
Result: The landscape created is not visible in level.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-67999 in the post.