Meshes not being rendered on iPhone 5, but working on any other iOS device

Hi!

For a minimalistic game I am using a simple shader which only has a color value, a texture and is affected by light sources:

 Shader "Simply Lit" {
     
 Properties {
     _Color ("Color", Color) = (1,1,1)
     _MainTex ("Texture", 2D) = ""
 }
 
 SubShader {
     LOD 150
     Lighting On
     ZTest Always
     Material {
         Ambient [_Color]
         Diffuse [_Color]
     }
     
     Pass {
         SetTexture [_MainTex] {Combine texture * primary Double}
     }
 }
 }

Everything is working on iPhone 4, 4s, 5s, 6, 6s as well as some iPads, but on the iPhone 5 the meshes with this specific shader are not being rendered. Does anybody know where the difference between the iPhone5 and all the other devices is? Or do you see a problem within the shader which might cause this problem?

Using the Standard shader makes the frame rate drop by a huge amount so I'd really like to use this very basic shader or a similar alternative.

Thank you very much in advance!! Maui