3D Text Mesh Shader Z Buffer Issue

I use some 3D Text Mesh with a simple quad mesh background as sign/panel. Now the z depth is not correct on the text, it is seen through the different panels. I've been testing in the shader with ZTest and ZWrite, but failed to find a solution to this. Can anyone help out?

 Shader "GUI/3D Text Shader 2" 
 { 
     Properties 
     { 
        _MainTex ("Font Texture", 2D) = "white" {} 
       _Color ("Text Color", Color) = (1,1,1,1) 
     } 
 
     SubShader 
     { 
            Tags { "Queue"="Overlay+1" "IgnoreProjector"="True" "RenderType"="Transparent" } 
            Lighting Off Cull back ZWrite Off ZTest On Fog { Mode Off } 
            Blend SrcAlpha OneMinusSrcAlpha
            Pass 
            { 
               Color [_Color] 
               SetTexture [_MainTex] 
               { 
                  combine primary, texture * primary 
               } 
            } 
     } 
 }