Symptoms
After migrating a library, the destination library doesn't have the library-level defined column default value settings. These settings differ from the column-level default value.
Details
the ShareGate migration tool doesn't preserve these settings during the migration.
To verify this setting open the library settings page and click on "Column default value settings."
Screenshot of the page on SharePoint 2013 :
Workaround
These settings need to be reconfigured at the destination.