Reproduction steps:
1. Open attached project "1187945_prefab_preview.zip"
2. Open "Prefab view bug repro scene"
3. Enter and exit Play Mode
4. In the Hierarchy, select the "Cube" object
5. In the Inspector, press "Open" to open the prefab in Prefab Mode

Expected result: Only the selected Cube prefab is seen in the Prefab Mode
Actual result: Another Cube from the Scene window is seen in the Prefab Mode

Reproducible with: 2019.2.0b1, 2019.2.13f1, 2019.3.0b11, 2020.1.0a13
Could not test with: 2017.4.34f1 (no Package Manager), 2018.4.13f1, 2019.2.0a14 (package errors)

Note: If the Hybrid Renderer package is deleted, Prefab Mode works as intended in 2019.2, 2019.3