GLSL phong shaders, debugging - opengl

Question

I am looking for some help debugging my GLSL phong shading code. Here is my vertex shader:
layout(std140) uniform Matrices {
mat4 model[1024];
};
layout(location = 0) in vec4 vertexCoord;
layout(location = 2) in vec3 vertexNormal;
uniform mat4 view; // from lookAt()
uniform mat4 projection; // perspective projection
out vec3 Position;
out vec3 Normal;
out vec4 lightPosEye;
void main() {
mat4 modelView = view * model[gl_InstanceID];
mat3 normalMatrix = mat3(transpose(inverse(modelView)));
//mat3 normalMatrix = mat3(modelView);
vec4 lightPos = vec4(350, 350, 350, 1);
lightPosEye = modelView * lightPos;
Position = vec3(modelView * vertexCoord);
Normal = normalize(normalMatrix * vertexNormal);
gl_Position = projection * vec4(Position, 1.0);
}
and here is my fragment shader:
in vec3 Position;
in vec3 Normal;
in vec4 lightPosEye;
layout(location = 0) out vec4 FragColor;
vec3 ads() {
vec3 Ka = vec3(0, 0.5, 0);
vec3 Kd = vec3(0, 0.5, 0);
vec3 Ks = vec3(0, 0.1, 0);
vec3 intensity = vec3(0.3, 0.5, 0.0);
float shininess = 0.1;
vec3 n = normalize(Normal);
vec3 s = normalize(vec3(lightPosEye) - Position);
vec3 v = normalize(vec3(-Position));
vec3 r = reflect(-s, n);
return intensity * (Ka + Kd * max(dot(s, n), 0.0) + Ks * pow(max(dot(r,v), 0.0), shininess));
}
void main() {
FragColor = vec4(ads(), 1);
}
Here is a screenshot of the result (I am also rendering the normals with another geometry shader for debugging purposes):
The artifacts on the cube are wrong, and the "shadows" on the circle also moves a bit when I move the camera around (change the view matrix).
Any obvious errors in my GLSL code?