If you turn off Explorer Replacement before running the installer, that should avoid problems opening Explorer and Control Panel if the installation goes wrong.
It's possible antivirus is blocking the newer binaries from being written if it doesn't recognise them. The other suggestions in Problems installing Opus may also be worth a try. Sometimes the same InstallShield issue can manifest in different ways, so they're all worth trying even if the error messages are slightly different.
Rebooting may also help. The new installer aims to reduce the need for reboots but they can still help (usually before running the installer).
Also, if Fast Boot is enabled in Windows (which it is by default, unfortunately), then pending file replacement does not happen if you do a shutdown and then turn the PC on again. It only happens if you Restart Windows while it's already running.
A screenshot of the error dialog may help tell exactly where it's coming from, if you still get the error and can save one.