Steps to repro:

1. Open attached project and 'Room_A' scene;
2. Open Lighting window (Window>Lighting>Settings);
3. Generate lighting for the scene;
4. Wait until the baking is finished;
5. Enter Play mode.

Expected result:
Meshes in the scene are rendered without artifacts (see attached expected.png screenshots).

Actual result:
Meshes are rendered with artifacts.
Regression introduced in Unity 2018.2.0a3.

Notes:
- Reproducible in 2018.2.0a4, 2018.2.0a3;
- Not reproducible in 2018.2.0a2;
- The issue is reproducible only after manually baking the scene; not reproducible after auto-bake;
- Reproducible only with Enlighten and Realtime GI; not reproducible with Baked GI and PLM;
- Reproducible in both Editor and Standalone Player.