Answer by Benjamin W. ·
The OS update is available on the 12.4.0 download page. You only need it if you download the separate Agent installer, not if you download the Enterprise Synthetic ISO file (it's in there).
You have to run it before installing an Agent.
So the installation order for the 12.4.5 Agent is:
12.4.0 OS Update
12.4.0 Enterprise Synthetic Agent
12.4.5 Enterprise Synthetic Agent
Agent Upgrade from 12.4 to 12.5.3 3 Answers
Error Getting VBE Interface! 1 Answer