Steps to repro:

1. Download attached project and 'SimpleReflectionprobeTest1' scene;
2. In the Lighting window enable 'Auto Generate' checkbox;
3. Wait until the lighting and reflections are baked;
4. In the Lighting window disable 'Auto Generate' checkbox;
5. In the Lighting window expand the dropdown list on the right side of 'Generate Lighting';
6. Click 'Clear Baked Data' window;
7. Observe the reflections.

Expected result:
The sphere in the center is black and doesn't reflect the scene.

Actual result:
The sphere in the center has reflections of scene rendered on it. See attached video.

Notes:
- Reproducible in 2018.3.0a8, 2018.2.2f1, 2018.1.9f1;
- Reproducible on both Windows 10 and OSX 10.13.6;
- The issue is not reproducible after going into play mode