To reproduce:
1. Open users attached project "DragPanelTest.zip"
2. Open "SampleScene.unity" scene
3. Enter Play mode
4. Press the white cube and drag the mouse, the cube should turn blue, release the mouse button and the cube should be white
5. Build for iOS
6. Deploy the Xcode project to an iOS device
7. Select the white cube and try to drag it for it to change color

Expected result: the same behavior as in editor, the cube turns blue when dragged
Actual result: nothing happens. Not even debugs are shown in the Xcode console

Reproduced on:
2017.4.0f12017.4.23f1 2018.3.9f1

Not reproduced on:
2019.1.0b6 2019.2.0a8

Notes:
Doesn't reproduce on Android, MacOS, Win10