The bug

When following a sequence of steps involving toggling fullscreen on and off while changing the fullscreen resolution, the following message is logged multiple times:

Error saving option GUI Scale: DynamicException[Value 5 outside of range [0:3] Optional[5]]

I stumbled upon this randomly, and am unsure if this exact sequence is the only cause of the issue.

How to reproduce

1. Navigate to Options -> Video Settings
2. Ensure the Fullscreen Resolution slider is set as far left as possible
3. Toggle Fullscreen on
4. Set the GUI scale to the highest possible (not Auto)
5. Toggle Fullscreen off
6. Set the Fullscreen Resolution slider as far right as possible
7. Toggle Fullscreen on
8. Set the Fullscreen Resolution slider as far left as possible
9. Toggle Fullscreen off
   The above error message is logged in the game log multiple times