The Installer doesn't rename the Mantainance.exe.new to Mantainance.exe on the first installation and after every update the Maintainance.dat.new will not replace the Mantainance.dat.
I recognized this problem already since many versions. But it happens only on Windows 10. In previous versions I didn't have this problem.
I can reproduce this error with the Qt Online Installer as well if I create a Custom Installer.