Solution : https://service.sap.com/sap/support/notes/1394758 (SAP Service marketplace login required)
Key words : 
31 system standstill nw pi 7, symptom sap jvm 5, java based products, java node shows, 11 solution sap jvm 5, sap jvm build 5, vm option -xx, reinitializes condition variables, timed wait operation, avoid lost notifications
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