To reproduce:

1. Download attached project "TestPP.zip" and open in Unity
2. Open "TestPP" scene
3. Ensure that Metal Graphics API is set as primary
4. Make sure that Bloom of Post-processing is enabled
5. Build for iOS
6. Deploy the Xcode project to the iOS device
7. Observe that lots of flickering white glitches appear in a Build

Notes:
- This issue does not reproduce on Windows Standalone, macOS Standalone, and Android (IL2CPP)
- This issue appears only on iOS platform with Metal Graphics API
- If OpenGLES Graphics API is set as primary, there are no white flickering glitches in a Build
- This issue appears when the Bloom of Post-processing is enabled
- This issue Video "WhiteGlitches.mov" is shared in the Comments section
- Could not check on Unity 2017.4 because project becomes corrupted
- Could not check on Unity 2018.1 because packages become corrupted
- Could not check on Unity 2018.3 and 2019.1 because of case 1098913. Stack Trace and Video "183flicker.mov" of this behavior are shared in the Comments section
- From other reports, it seems that this issue is still reproducible on Unity 2018.3.0b9

Tested with:
- iPhone 7s Plus, iOS: 12.0 - Reproduced

Reproduced on Unity 2018.2.11f1, 2018.2.16f1 and 2018.3.0b9
Could not check on Unity 2017.4, 2018.1 and 2019.1 because of above-mentioned problems