Materials Turn Black On Scaling

I am using ARCore 1.12. I wanted to show building or a house in AR. The scale of the the house is so huge so I am scaling it when I instantiate it to fit the screen using mesh.bound. But the model is appearing black when it instantiate. As you can see the images down below I can just create this in Unity Editor. You can see the scale on which it turns black. But some model does not show this behavior. I want to know if this problem is related to the scale factor of the model?Or it is some other thing? I have been stuck for the past two weeks and couldn't find the solution.

Here is the video which describe the problem clearly.
https://drive.google.com/open?id=1BIE6yGmC5lHUF408Ldb8ZwkhnW2Awrs_

 

Is it related because of the scale difference when exported from the 3d modeling software?

 

You can adjust the scale of imported models on the model file itself (FBX, OBJ, etc.) by setting the Scale Factor. Having a scale that small could have adverse effects.

You may also want to check if you have a material on the object, and whether there is any lighting in the scene.

 

Yes, By decreasing the scale factor of the model does improve the viewing on different scales but it also decreasing the original real world size of the model too. I have also find out that when in the editor when the model turns black then I changed the shader from Standard to Unlit->Color and the color appears.

 

Can you suggest some other solutions?