It is possible that after running the migration script from 4.1 to 5 an error occurs regarding a table treport_content:
ERROR 1452 (23000) at line 266: Cannot add or update a child row: a foreign key constraint fails (`pandora`.<result 2 when explaining filename '#sql-867_1ba'>, CONSTRAINT `?sql?867_1ba_ibfk_1` FOREIGN KEY (`id_report_content`) REFERENCES `treport_content` (`id_rc`) ON DELETE CASCADE ON UPD)
If this occurs, you will have to execute this query in MySQL:
DELETE from treport_content_item WHERE id_report_content NOT IN (select id_rc from treport_content);
After this you have two options: to comment all lines to 265 and re-run the migration script, or to restore the database using the backup that we should have done before, run the previous query and then execute the full migration script again.