Install from Login Script worked once, now does nothing

I have added lines to my login script as follows:

IF EXIST "C:\Program Files\ESET\ESET NOD32 Antivirus\egui.exe" GOTO NEXTSECTION
\\<servername>\esetinstall$\einstaller.exe​

This worked once, and installed ESET on a test computer. I manually uninstalled ESET to test the script again, and it will no longer install.
What gives? How can it work once, and not ever again?
I have confirmed that egui.exe is not present when it runs the subsequent times.
Thanks.

 

After a successful installation, ERAS remembers that installation has already completed successfully on the target machine and does not attempt to push it whenever einstaller is run.

 

That's clever.
Is there a way to unflag this, so I can continue testing with this one computer?

 

Spoke with Business Support. They told me that there's no way to work around this. The einstaller.exe actually checks a Registry Key to decide if it needs to run again. Uninstalling ESET (doesn't matter how) leaves the Registry Key intact, so einstaller.exe doesn't see the need to do anything.
This seems like a bug to me. If the application is uninstalled, the Registry Key should be removed also.
I'm looking to have a way to guarantee that ESET is on a system, particularly in cases where technicians forget to reinstall if they were working on the system and uninstalled for some reason, but also if an end user figures out the uninstall password.