The issue is fixed in the latest version of GearVR, which you’ll need to update, and you’ll need the code in 4.13.1 to go with it. That’s being released soon. The issue required a fix in the Oculus MobileOVR SDK to fix a race condition that was caused by the way UE4 initializes the renderer.
If you want the fix early, you can grab this commit: https://github.com/EpicGames/UnrealEngine/commit/6cba49a0bf88ab6a4c2d0ae66e9f7d1273a82893 , as well as making sure you update your GearVR runtimes on your phone to the latest.