Error while restoring a domain or during a migration: filemng: Error occurred during /usr/bin/base64 command

Symptoms

An error appears in /usr/local/psa/PMM/rsessions/<session_id>/migration.log while restoring a domain or during a migration:

CONFIG_TEXT: </web-settings><composer-instances>
<composer-instance path="httpdocs/wp-content/plugins/jetpack/composer.json"/>
</composer-instances></subscription-info>
<stderr>filemng failed: filemng: Error occurred during /usr/bin/base64 command.

Cause

A WordPress plugin was removed, its composer.json was not found during the backup restoration. This is a Plesk bug with ID PPPM-7222 which will be fixed in future updates.

Resolution

This error can be safely ignored. Or as a workaround, do the following whenever some WordPress plugin is removed:

1. Press Scan button at Subscriptions > example.com > Applications. It will synchronize changes with Plesk database.
2. Create a new backup at Tools & Settings > Backup Manager.