Just FYI in case anybody faces a similar issue - there was a program error. After the implementation of these notes, all works fine:
| 1910458 | Update via position management does not work correctly |
| 1912233 | Subsequent note to SAP Note 1910458: update FDC1 via position management |
| 2169045 | Termination RQ 899 E_WRONG_PARAMETER when reconstructing using transaction FDFD. |
| 2178859 | Supplement to SAP Note 2169045: RPTM_CM_UPDATE |