To reproduce:
1. Open attached project;
2. Open "repro" scene;
3. Make sure DX11 is the main Graphics API (Edit > Project Settings > Player > Other Settings);
4. Switch Graphics API to Vulkan;
5. Take a look at the terrain

Expected result: height of the terrain is correct after changing API;
Actual result: terrain is rendered as plane with terrain's textures.

Reproduced in: Universal RP 7.1.1, 7.1.2 + Unity 2019.3.0b7, Unity 2019.3.0b8

Note: tried reproducing it with creating a new terrain - the issue doesn't reproduce anymore.