Reproduction steps:
1. Open project in "draw_mesh_now2.zip"
2. Switch Graphics API to OpenGL ES 2 or 3
3. Build for iOS and deploy the project
4. Press the "Click me" button

Expected result: Nothing happens (just like in Editor)
Actual result: Projection Matrix gets corrupted and the Sprite (red) gets rendered on the entire screen

Reproducible with: 2018.4.25f1, 2019.3.0a1, 2019.4.5f1, 2020.2.0f1
Could not test with 2020.2.0a16, because OpenGL ES is deprecated (screen blinks after pressing the button when using Metal)

Reproducible with OpenGL ES 2 and 3
Result with Metal: Pressing the "Click me" button makes the screen blink

Devices tested:
Reproducible with:
VLNQA00015, Samsung Galaxy Note8 (SM-N950W), Android 8.0.0, CPU: Snapdragon 835 MSM8998, GPU: Adreno (TM) 540
VLNQA00310 iPad Pro 12.9 1st gen (iOS 13.4.1)
Could not test with:
VLNQA00204 iPhone 5C (iOS 10.3.3) because Xcode could not install Application

Notes:
1. The issue has a workaround: enabling the second Camera before pressing "Click me"
2. Not reproducible in Editor (tested Metal and OpenGL Core)
3. When using Metal the screen blinks (tested iOS)
4. The script that is executed upon pressing the button is attached as an image below