While upgrading from 11.3.5 to 11.3.6 SP1 on windows, an old database which was no longer online was still appearing on the database credentials window and of course the upgrade was failing.
This old database was commented out in the instance config file with a "#"
It appeared in the trace of the upgrade that the installer was still processing this commented out line.
1 - Remove the entire line of this non-active database from the instance config file
2 - Append additional "#" before "#EventServer_2" (##Eventserver_2)
Check the attached document for more details.
Sustaining Engineering is working on a code fix.