Terrain and Lights doesn't work on Android

I’m having some troubles using Terrain and Direction Light on Android Device, here’s the scenario: i have a simple terrain, my player, an npc and a direction light. On PC it runs normal, on an LG L9 (Android 4.1.2) it runs normal, on Sony Xperia U it runs but the terrain isn’t affected by the light BUT when i push the lock button the terrain gets affected by the light but, obviously, the screen goes down Any ideas?

As per my information, Unity Terrain are not optimized yet for mobile devices (in your case android devices), so its recommended to avoid using terrain for mobile devices, you can see Free complete project : Penelope, from asset store. in that you can find documentation and full example of the scene, For achieving terrain surface you have to make them in 3d modelling tool like Blender3D, and everything you can divide into 1000 vertices for each poly surface and use iphone shader for uv lighting and tiled based texture. And you will be able to create optimized environment in Unity 3D for mobiles.
I hope this gives you some direction. You can achieve enironment in 10-15 draw calls, which will work very smoothly on mobile devices.
In case you face any problem, you can ask me anytime.
Thank you.