Reproduction steps:

1. Open "test_2018.zip" project
2. Open "test" scene
3. Enter Play Mode
4. Click on the Game Screen
5. Select the "Main Camera" in the Hierarchy window
6. Change the "Clipping Planes" value "Near" to '0.3'
7. Click on the Game Screen
8. Look at both the created Cubes
9. The first cube (Usually) has 2 x 2 lines
10. The second cube (Usually) has 11 x 11 lines

Expected Result: "Debug.DrawLines" draws 11 x 11 lines
Actual Result: "Debug.DrawLines" draws an uncertain amount of lines, because some of them overlap, due to "ViewportToWorldPoint" inaccurate calculations

Reproduced with: 2019.1.0a2, 2018.3.0b3, 2018.2.10f1, 2018.1.9f2, 2017.4.12f1|

Note:
Changing lines 54 and 55 in "testTransform" script from "... * 0.0001f;" to "... * 0.01f;" fixes the issue