Need to delete service before upgrade?

1. Brekeke Product Name and Version:
Sip 3.9.5.5
2. Java version:
jre 1.8.0_161
3. OS type and the version:
Windows server
4. UA (phone), gateway or other hardware/software involved:
N/A
5. Your problem:
I'm testing an upgrade from version 3.9.5.5 to the latest 3.9.5.8. I stopped the Brekeke service, got an sst backup through the web UI and copied the sip directory from under webapps, then ran the 3.9.5.8 installer as admin.
Part way through I got a 'Failed to install Brekeke SIP service.' error.

In the service-install.log I found:

Install failed: 8 The specified service already exists.

Failed to install service.

Do you need to delete the Brekeke service before upgrading as well as stopping it?

Have you uninstalled the existing Brekeke SIP Server?
If so, let you restart the Windows.

I didn't uninstall it completely, I don't understand why I can't do an in place upgrade? Also, This is a Java webapp running in Tomcat, surely you only need to restart Tomcat? Why do you need to reboot Windows?

You don't have to use an installer if it is a minor version update.
Just upload the sip.war file at [Update Software] page.

For updating Tomcat web server, uninstall the Brekeke SIP Server completely, reinstall it with the installer and restore the copied directory.

A rebooting Windows will clear resources the service held.