Solution : https://service.sap.com/sap/support/notes/429481 (SAP Service marketplace login required)
Key words :
system generates message fwtm136, attached source code corrections, additional key words wtmg, conversion step 'convert customizing', 'convert customizing' step, internal table i_t042b, extended withholding tax, transaction wtmg, withholding tax, 'table t042b
Related Notes :
| 504442 | WTMG: red traffic light in 'Convert documents' zero amount |
| 390148 | WTMG: Composite note for withholding tax changeover |