The error message "'utf-8' codec can't decode byte 0xfa in position 60: invalid start byte" suggests that there might be an issue with character encoding in a configuration file related to Plesk's Backup Manager.

To address this issue, you can try the following steps:

1. Check System Locale:

   • Verify that the system's locale settings are correctly configured. In particular, ensure that the default character encoding is set to UTF-8.

2. Examine Configuration Files:

   • Look into the configuration files related to Plesk's Backup Manager. Specifically, focus on any files that might store settings related to character encoding.

3. Check Backup Manager Logs:

   • Review the logs specific to Plesk's Backup Manager (usually located in /var/log/plesk/PMM/) for any error messages or warnings related to character encoding.

4. Check for Recent Changes:

   • Consider if any recent changes or updates were made to Plesk or the server that might have triggered this issue. Reverting any recent changes might help resolve the problem.

5. Check for Special Characters in Backup Names:

   • Ensure that there are no special characters or non-standard symbols in the names of your backups. Special characters can sometimes cause encoding issues.

6. Verify Disk Space:

   • Ensure that there is sufficient disk space available on the server. Lack of space can sometimes lead to encoding errors.

7. Check for File Corruption:

   • Verify if any configuration files related to Plesk's Backup Manager have become corrupted. If so, you might need to restore them from a backup or reinstall Plesk.

8. Update Plesk:

   • Make sure that your Plesk installation is up-to-date. If the issue is related to a known bug, it might have been addressed in a newer version.

9. Contact Plesk Support:

   • If none of the above steps resolve the issue, consider reaching out to Plesk support for further assistance. They can provide specific guidance based on your server's configuration.

Remember to always back up your data and configurations before making significant changes or updates to ensure you can revert to a stable state if needed.