Solution : https://service.sap.com/sap/support/notes/1591363 (SAP Service marketplace login required)
Key words : 
solution apply abap patch listed, terms trex_ext_load_history trex reason, symptom function module trex_ext_load_history, function module needed, prerequisites
Related Notes : 
       
| 1594611 | BWA 7.20: Revision 12 | 
| 1564568 | BWA monitor: Incorrect check for BWA overload |