My outline shader gets covered by the background at certain angles.

I am working with VRTK and SteamVR in Unity 2018.2.5f1. I recently created some sphere objects that float in the air. These objects use an outline shader provided by VRTK. In the first image you can see the sphere being outlined in white. This is how I expect it to look all of the time.

But recently I have opened my project and now when the camera is at certain angles the shader will seemingly change its properties or become obstructed by an object that is behind it. Effectively making it invisible as shown in the next image.

This is all happening within the editor and within my Vive headset. Although when loading into the VR simulator included with VRTK the object appears as expected. When I first created these objects I did not have this issue, I believe I adjusted a setting I perhaps shouldn't have and now I don't know what it could have been. I am hoping I can find some suggestions here. I've spent more time than I wanted to on this. :(

Can anyone help me fix this hole I shot in my foot? :P

Thanks in advance.