Install an application (online example) in a directory which needs admin rights.
E.g. "C:\Program Files (x86)\..."

Then do the update process from this directory. The application will fail doing the installation, with the first writing file with a msg box pop up: "that a certain file cannot be written (retry, ignore, cancel)"

The installation process will fail, but the current installation is in a messed up state. The installer has to be killed via task manager..

Remark: Admin rights was gained during install from QtIFW, but it fails anyway...

This is a blocking issue!