Hi -
The only way I can get this to reproduce is to have two box capture actors with no fade distance (fade set to 0) close enough and expansive enough to overlap and they will create the line.
Here is an image:
I have also attached my 4.8.3 project with this setup, if you still think that this is still an issue open this test project up and attempted to reproduce the setup with the assets in the project and re-upload here.
Thank You -
Eric Ketchum
[Test Project 4.8.3][2]