How to reproduce:
1. Open the attached 'ShadowmaskLoadStoreActions.zip' project
2. Switch Platform to iOS and enable Development Build in Build Settings
3. Build for iOS and open the Xcode project
4. Go to Product > Scheme > Edit Scheme
5. Set Metal API Validation to Enabled
6. Set GPU Frame Capture to Metal
7. Deploy project to an iOS device
8. Click the camera button in Xcode's debug bar
9. Navigate to Camera.Render/Drawing/Render.OpaqueGeometry/RenderDeferred.GBuffer

Expected result: Clearing render pass is executed only once
Actual result: Two additional clearing render passes are executed

Reproducible with: 2019.4.11f1, 2020.1.6f1, 2020.2.0b3
Couldn't test with: 2018.4.27f1(no GBuffer render passes in Xcode)

Reproducible with:
iPhone 8+ (iOS 12.0)
iPhone XR (iOS 13.4.1)
iPad Air 2 (iOS 11.0.3)

Could not test with:
iPad 9.7 6th gen (iOS 14.0b7) (Consistently crashes on Frame Capture)

Note:
- Not reproducible with Lighting Mode Subtractive