Solution : https://service.sap.com/sap/support/notes/1095903 (SAP Service marketplace login required)
Key words : 
terms bapi background dialog box reason, alm-bapi downgrade kit, order xy work centers, missing capacityfurther processing, relevant correction instructions, capacity overload occurred, dialog boxes, release order, capacity check, availability check
Related Notes : 
       
| 1062653 | BAPI_ALM_ORDER_MAINTAIN processes status popup incorrectly | 
| 894799 | Module CO_ZF_CHECK_SUBNET is not without dialog II | 
| 775538 | BAPI:Dialog box or dump DYNPRO_SEND_IN_BACKGROUND at release | 
| 708508 | Downgrade BAPI_ALM_ORDER_MAINTAIN -> errors |