A new version of the NACVIEW system is now available. Version 2.3.18 introduces many expected fixes and improvements.
One of them is the changed mechanism for upgrading the system to a newer version.
Before upgrading NACVIEW to the new version 2.3.18, for each node of the NACVIEW system from the CLI level, select option 7 - NACVIEW update installer.
Then the system node must be restarted.
After restarting, the update process can continue normally: