LineRederer with corner vertices display positions in wrong location

I'm trying to create display a raycast with a line renderer. Every time the raycast reflects I'm adding a point to the line renderer, but I'm having a problem with the width of the line:
Adding corner vertices fixes the width problem but creates another:
Changing the number of vertices doesn't help either. I don't know how to use a mesh renderer and definitely not how to create my own line renderer. What can I do?

I'm using the Unity 2020.1.0b8.3654, on Windows 10 if that matters.