Steps to reproduce:
1. Open the attached project (BugProject.zip)
2. Switch platform to Windows Store
3. Add BugScene to build
4. Build for WSA Universal 10 SDK, Build type - D3D (Where touch input is supported)
5. Swipe your finger across the red area, OnDrag is working ("Drag" text will appear)
6. Set CursorLockMode.Locked by turning toggle on (white area, under the “CURSOR LOCK” label)
7. Swipe your finger across the red area, OnDrag is not working ("Drag" text will not appear)

Incorrect Expected result: OnDrag should be invoked with touch input
Expected result: When cursor is locked OnDrag is not invoked with "mouse like" input (Mouse, Stylus, Touch)

An object's OnDrag event is tied to mouse input, which in this case is simulated from a Touch source, but when the cursor is locked mouse movement is disabled and the cursor hidden making "dragging" operations inoperable. The reason is: locking the cursor allows the camera to be moved around without the cursor getting in the way. Even with Touch, the typical scenario for locking the cursor is to move the camera via swipe gestures rather than dragging an object.

Note that interactions with objects via Touch can still be performed (with a locked cursor) by processing the Input.Touches data directly.

Actual result: OnDrag does not invoke with touch input

Note:
Unable to test with 5.4
Works as expected in Android

Reproduced with: 5.5.3p1, 5.6.0f3, 2017.1.0b1