We are talking to BMC and it sounds like 8.1 isn't a good match for running on 2012 or 2016 so this is very hard to troubleshoot. BMC L3 team is going to try to install in their Dev environment. If it doesn't work, we will find a different path forward such as in-place upgrade to 9.1.04 first and then 19.02. I'm still happy to hear if anyone has had success installing on 8.1 Windows 2016 or encountered and overcame similar issues.
I have had no issues with 8.1.x on Server 2012 (not tried 2016).
Are you running the installers as Admin by right mouse clicking and using "Run as Administrator", although you are logged in as a local administrator?
Hi Carl! Yes, we're running as Admin.