Fixed this issue -
1. Persist "processInstanceId" once process starts.
2. Load "process instance id" and send signal.
// Signal timer event,
kSession.signalEvent(type, event, processInstanceId);
Note - No need to load old session - Don't do this
JPAKnowledgeService.loadStatefulKnowledgeSession
Check process_instance_info table, if process terminats due to server crash, you would find records there. Sending signal with given process intance id will resume process.
Job Done!!