Based on our investigation, the issue is caused by the following:
Root Cause: The old version of the plugin was not completely uninstalled (the fs and pt services were still running). During the installation of the new version, the system attempted to connect to the old plugin services, resulting in error #4 (Invalid parameter).
Solution:
Check the status of plugin services on the client;
Uninstall both the old and the current new version of the plugin;
Ensure that the fs and pt services are stopped;
Reinstall the new version of the plugin.
After performing these steps, the backup should run successfully.
