Steps to reproduce:

1. Download and import attached project. (case_767748-CellStage - REPRO.zip)
2. Open scene lobby.
3. Play.
4. Press button or host a server.

Expected result: Scene is loaded and objects are visible because Ambient light from skybox.
Actual result: Everything is black. Ambient from skybox and Reflections from skybox are not visible on objects.

Notes: On build everything seems to work fine, bug only occurs when played in editor. Ambient works fine when source is color or gradient. Does not work when scene is loaded both manually or through network.

Reproduced on: 5.4.0b5, 5.3.2.p3, 5.2.4f1, 5.1.4f1.