How to reproduce:
1. Open attached project ("LineRendererNotDissapearingBug.zip")
2. Enter Play Mode
3. In Hierarchy, delete "Target" GameObject
4. Observe Scene or Game view

Expected result: All LineRenderer lines have changed their startWidth and endWidth values
Actual result: Some of the LineRenderer components did not change their startWidth and endWidth values

Reproducible with: 2018.2.0a6, 2018.1.0b13, 2017.4.0f1, 2017.3.2f1, 2017.2.2p1, 2017.1.3p2, 5.6.5p2

Note:
In order to bypass the issue, you have to change LineRenderer Alignment to View and then move or rotate the camera in Scene view