Solution : https://service.sap.com/sap/support/notes/453997 (SAP Service marketplace login required)
Summary : 
      In SAP transaction MIRO, certain fields such as BEWAR, BWTAR, EBELN, EBELP, among others, do not retain values upon parking or canceling posted invoices due to a program error. The solution involves hiding these fields in the general ledger block as they either update materials management or are country-specific and unsupported. Field ZUONR remains editable and is updated in the system for parked or canceled documents. The fix for this issue will be included in R/3 Support Package for Release 4.6C and has been corrected in Release 4.7. Manual adjustments involve modifying the COBL_MRM dictionary structure to include ZUONR.
Key words : 
nplnr           nplnr      vornr           vornr      zuonr           dzuonr <---- insert, change dictionary structure cobl_mrm, changing dictionary structure cobl_mrm 1, systen supports fields menge, insert field zuonr, activate structure cobl_mrm, general ledger block, similar problem occurs, financial budget item, partner profit center
Related Notes : 
       
| 752240 | |
| 510662 | |
| 447783 | |
| 446453 | MIR7:error KI249 during account assignment to network | 
| 422072 | |
| 403159 | |
| 402834 | Supplement to Note 391683 | 
| 398937 | MIRO: Not supported fields in the general ledger block | 
| 391683 | MIRO: Fields on the G/L account tab |