The issue happens on some devices on all iOS versions.

Steps:
1. Build and Run attached project (TestDisplay.zip) for iOS
2. In player: press Effect On > Open > Close (try multiple times)

Result: player screen (background) becomes black.

Reproduced with: 2018.1.0a6, 2017.2.0p1, 5.6.4p3.
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Test results:
iPad 3 - 9.3.5 - not reproducible
iPhone 5C - 9.3.2 - not reproducible
iphone 5 - 10.1.1 - not reproducible
iPhone 6S - 11.0 - not reproducible
iPhone X - 11.0.1 - not reproducible

iPad Mini 2 - 9.2.1 - reprodcible
iPad Mini 4 - 9.2.1 - reprodicble
iPhone 5S - 9.3.3 - reproducible
iPod 6th gen - 10.2.1 - reproducible
iPad mini 3 - 10.3.2 - reproducible
iPad mini 2 - 11.0 - reproducible

Motorola Nexus 6 - Android 6.0.1 - not reproducible
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Note: not reproducible on Android.