Solution : https://service.sap.com/sap/support/notes/648630 (SAP Service marketplace login required)
Key words : 
terms stxh reason, respective sales order, sales order, sales orders, individual order, process orders, system checks, identical text, prerequisites notes 309580, solution implement
Related Notes : 
       
| 607084 | Releasing text memory after assembly order creation | 
| 561529 | Missing long texts for order header, operation, component | 
| 519373 | Various function groups are loaded unnecessarily | 
| 429414 | Production memo not printed in other language | 
| 309580 | Productn memo does not come from contract rel.order |