When doing a pre-migration check or copying content, one of the following messages is displayed:
When migrating content, it's strongly recommended to have 'Full Control' permissions on your source list.
When migrating content, it's strongly recommended to have 'Full Control' permissions on your destination list.
To ensure that your migration works as expected, Sharegate needs to have access to some information that requires different permissions in SharePoint. Because the necessary permissions can vary depending on migration settings and on the SharePoint environment, we recommend using Full Control as it will include all necessary permission levels.
Grant Full Control permissions to the user performing the migration both on the source and the destination lists.