First noticed this under the audio settings, if you change values then click "Reset" without clicking "Apply" it doesn't actually reset any of the sliders.
No sliders are reset
Doesn't reset VSync or Resolution options
Doesn't look like anything on this anything on this tab gets reset. I only tried a subset of the keybindings but none of those I tried actually reset. This screen seems the most crucial for the reset to work.
None of the settings on this page reset either.