Solution : https://service.sap.com/sap/support/notes/745916 (SAP Service marketplace login required)
Key words :
internet applications solution import, previous entries disappear, relevant support package, siac_convert_from_4x report, user-unfriendly, initial screen, error messages, exited completely, successful execution, individual object
Related Notes :
774148 | SIAC_CONVERT_FROM_4X: Overwriting existing objects |
678904 | ITS - New storage structures as of SAP Web AS 6.40 |