Enabling Reflection Probe Box Projection in the GraphicsSettings results in a cross of thin, sharp lines. Without Box Projection, rendering is fine. The lines are view dependent, but always horizontal and vertical.
When applying a metallic/normap map, the thin lines become wide streaks of flickering random pixels.

Steps:
1. Open attached project ("ExxonDebug.zip")
2. Switch platform to iOS or Android
3. Graphics Settings > check Box Projection for all Tiers
4. Build and Run
5. In Player navigate/zoom closer to the plane, viewing it exactly from the front (use drag&pinch gestures)

Result: thin, sharp lines are visible while navigating in the Player.

Reproduced with: 2018.1.0a1, 2017.1.2.p2, 5.6.4p1.

Tested with:
1) iPad mini 4 iOS11.0
2) iPad mini 4 iOS9.2.1
3)Motorola Nexus 6 Android6.0.1

Note: I was unable to reproduce the issue in the Editor / Standalone.