Clicking the Override option when attempting to replace a keyboard shortcut with another key that is already bound will not update the settings.
Workaround:
Unbinding the key before rebinding it to the new shortcut will allow the new setting to be accepted.
Regression:
No - The same behavior exists in 4.13.2
Result:
Pop up window closes but shortcut setting is unchanged
Expected:
Z is set as Forward and FOV Zoom Out becomes unassigned
Head over to the existing Questions & Answers thread and let us know what's up.