When using Windows 10 it might happen that after flashing (or before) errors occur. We've discussed this with the etcher.io team, and they have applied several fixes to etcher. As you may know the KiOS installer is forker from Etcher.io, so this means that to fix this issue we need to merge with their root repository.
As the installer is not our main priority, and to be honest developing it cross-platform isn't that straight forward. We propose another solution (thanks Spongebob Brandon), to run the installer as Windows 7.
- Navigate to the install directory (ie. C:/Program Files/KiOS or C:/Program Files (x86)/KiOS)
- Right click KiOS.exe and select Properties
- Select the Compatibility tab
- Check the "Run this program in..." and in the dropbox select "Windows 7"
- Click OK