Steps to reproduce:
1. Open attached project (OC link)
2. Load Scene Scene_Experimental 1
3. Enter Play mode

Expected result: no glitching
Actual result: texture glitches (gif attached)

Reproduced with: 5.6.4f1, 2017.1.1f1, 2017.3.0f3, 2018.1.0b7, 2018.2.0a3

Note: this problem does not appear in a built project
Note2: The project contains some scripts not supported by 5.6 but the issue can be seen by resizing the Game Window without entering Play mode