To reproduce:
1. Open project attached by QA
2. Enter playmode
3. Click left mouse button to decrease resolution

Note: Right mouse button click reverts to original resolution.
This is reproducible both in the Editor and with Mac Standalone build.

Expected result: Resolution is being decreased without any additional issues
Actual result: Artifacts appear

Reproduced with: Unity 2019.1.0a13, 2019.1.0a12
Not reproducible with Unity: 2018.3.0f1, 2019.1.0a10

Hardware: Macbook Pro 2017
CPU: 3,1 GHz Intel Core i7
GPU: Radeon Pro 560 4096 MB
Intel HD Graphics 630 1536 MB

NOTE: Reproducible only on external (AMD) GPU. Intel GPU works as expected.