How to reproduce:
1. Create a new project or open an existing one
2. Set the Field of View field of the Scene Camera to a number lower than 179
2. Observe how the grid is rendered
3. Set the Field of View field of the Scene Camera to 179
4. Observe how the grid is rendered again

Expected result: Scene view's grid position on its axis stays the same
Actual result: Scene view's grid position is inverted on its axis

Reproducible with: 2019.1.14f1, 2019.2.4f1, 2019.3.0b1, 2020.1.0a2

Notes:
Changing the grid's axis will also change the axis on which it is inverted.
Until Unity 2019.3 it was not possible to change the grid axis, therefore, the issue was only reproducible on Y-axis.
The issue was not reproducible until Unity 2019.1 as there was no way to change the Field of View of the Scene Camera.