How to reproduce:
1. Open user provided project
2. Build and run on device
3. Start the game
4. Click on the cactus in the top left and try to place it.
* Clicking the cactus in editor highlights it meaning it gets selected, which doesn't happen on device.

Expected behaviour: Touch inputs on 'OnMouseDown' events get registered
Actual behaviour: Click is not registered

Reproduced with: 5.6.0a3, 5.6.0b7
Not reproduced with: 5.5.0p4, 5.5.1p2, 5.6.0a1

Devices Under Testing:
Reproduced with:
Samsung Galaxy S5 Neo | Android 6.0.1
LG Nexus 5X | Android 7.1.1