Steps to repro:

1. Download the project: https://oc.unity3d.com/index.php/s/II0t8SQHea5a8tq
2. Open 't1' scene;
3. Open Profiler window (Window>Profiler);
4. In the left panel of the Profiler window select 'Memory' tab;
5. Launch the scene;
6. In the Profiler window notice and remember 'Meshes' field number;
7. Exit Play mode;
8. Launch the scene again;
9. Observe 'Meshes' number in the Profiler window.

Expected result:
Mesh number is the same.

Actual result:
Meshes number increases after reloading the scene invoking inevitable memory leak. See attached video.

Notes:
- The issue is reproducible only when Realtime GI is checked in the Lighting settings window; doesn't reproduce with Baked GI;
- Reproducible in 2018.2.0a1, 2018.1.0b4, 2017.3.0p2, 2017.1.2f1;
- Reproducible on Windows and Mac;
- The issue is stably reproducible in Editor; could not consistently reproduce in Standalone player, yet for user it did repro in Windows and PS4 Standalone player (see initial user comment);
- The issue happens only when there is at least one static object in the scene, it doesn't happen when all objects in the scene are dynamic.