Reproduction steps:
1. Open the attached “BugRepro” project
2. Open the “Assets/Scenes/Dev” Scene
3. Enter Play Mode
4. In the Game View, click the “Play” button
5. In the Hierarchy window, select “GameConfig” GameObject (Core > Game > GameConfig)
6. In the Inspector window, change the “Physics Step” script's Gravity X variable to 1
7. Save the subscene (Ctrl/Cmd + S)
8. In the Game View, observe the terrain

Expected result: The terrain remained the same shape
Actual result: The terrain became flat

Reproducible with: 6000.0.0b16
Couldn't test with: 2021.3.37f1 (Entities package is not supported), 2022.3.36f1, 2023.2.19f1 (compilation errors in the Console),

Reproducible on: Windows 11
Not reproducible on: No other environment tested

Note: This is only one of the ways to reproduce the issue, it can also be reproduced by recompiling a shader, saving a VFX Graph or a Shader Graph