Occasionally some files can become corrupt with strange results. One temporary solution can be to backup and delete the Setting folder. The backup is helpful in case this fix works, so that the state of the corrupt Setting folder can be examined to fix the bug.
Use the following steps to navigate to the Setting folder and complete the task.
Close the game.
Press Windows Key + R
In the entry box type %userprofile%\appdata and press enter, or click OK
In the new window navigate to C:\...\appdata\Local\Ironclad Games\Sins of a Dark Age\
To make a backup and delete from here, right click on the Setting folder and select CUT. Navigate to your preferred backup location, right click within the backup folder and select PASTE.
The next time the game is launched, it will generate a new Setting folder.