Solution : https://service.sap.com/sap/support/notes/205909 (SAP Service marketplace login required)
Key words : 
additional key words fcode_wiar, function 'cancel technical completion', symptom termination message_type_x, field selection control, required entry field, abap program written, created purchase requisitions, shortly cancel, purchase requisitions, ' purchase requisitions
Related Notes : 
       
| 397290 | MESSAGE_TYPE_X when cancelling technical completion | 
| 372544 | Termination 00055 when resetting technical completion | 
| 324028 | Transfer of changed fields from PReq to activity | 
| 312135 | CN22/IW32/CO02: Purchasing data is initialized | 
| 182008 | Required entry field Price not copied from PReq |