My control setting are all normal except my Sprint button is set to "Left Shift" and my crouch is set to "Left Ctrl"
How to duplicate:
1. Press Left Shift to begin Sprinting
2. While Left Shift is pressed and you are running press the 2 key
3. Notice how the inventory indicator doesn't switch to that slot but does change to other slots.
If any other information is needed please notify me and I will do so.