Steps to reproduce:
1. Open attached project "911008.zip"
2. Build "test" scene for UWP
3. Open VS solution
4. Build & Deploy on local machine
5. Place the cursor anywhere on the screen but the centre
6. Press left mouse button (without moving the mouse)
*cursor gets locked and mouse movement rotates the camera while holding down the button*

Expected result: Mouse X and Mouse Y axies return actual mouse input values (like in Editor)
Actual result: Mouse X and Mouse Y axies return invalid values in the first frame after locking cursor making cameras rotation to 'jump'

Not reproducible on Editor

Reproducible with: 5.5.3p3, 5.6.1p1, 2017.1.0b5