Thanks for your guidance but,

Even though I triggered the Custom Action at the Finish Dialogs Stage, I encountered the following error when attempting to move the log file:

"The file is being used by another process."

This issue likely occurs because the Microsoft Installer (MSI) locks the log file during the installation process. In response, I tried copying the log file instead of moving it, with a 2-second delay before the operation. However, the log file still contained incomplete data.

The likely reason for this behavior is that MSI continues to write to the log file until the entire installation process, including the MSI session, has fully closed. Since the Custom Action is triggered before the MSI process completely shuts down, it’s possible that not all log events are captured by the time the log file is copied.