Steps to reproduce:
1) Open the attached project.
2) Build and deploy to an iOS or Android device.
3) Locate the button labeled 'Broken', aim at it and tap the screen.

The button should be pressed and play a sound, however it does not. Removing the Event Trigger component from the Cube (which is the parent to Canvas) makes the button clickable.
This issue does not appear on the Editor.

Reproduced on:
5.5.0a5, 5.4.0p1, 5.3.6f1

Devices:
iPhone 6+ iOS 8.0
LG G4 Android 6.0