11:58:40.972 [main] ERROR org.camunda.bpm.engine.context - ENGINE-16004 Exception while closing command context: null 
java.lang.NullPointerException: null
at java.base/java.lang.String.compareTo(String.java:1196)
at org.camunda.bpm.engine.impl.db.entitymanager.operation.comparator.DbEntityOperationComparator.compare(DbEntityOperationComparator.java:39)
at org.camunda.bpm.engine.impl.db.entitymanager.operation.comparator.DbEntityOperationComparator.compare(DbEntityOperationComparator.java:28)
at java.base/java.util.TreeMap.put(TreeMap.java:550)
at java.base/java.util.TreeSet.add(TreeSet.java:255)
at org.camunda.bpm.engine.impl.db.entitymanager.operation.DbOperationManager.addOperation(DbOperationManager.java:81)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.performEntityOperation(DbEntityManager.java:630)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flushCachedEntity(DbEntityManager.java:508)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flushEntityCache(DbEntityManager.java:474)
at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flush(DbEntityManager.java:292)
at org.camunda.bpm.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:272)
at org.camunda.bpm.engine.impl.interceptor.CommandContext.close(CommandContext.java:188)
at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:119)
at org.camunda.bpm.engine.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:72)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
at org.camunda.bpm.engine.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:70)
at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(ProcessApplicationContextInterceptor.java:70)
at org.camunda.bpm.engine.impl.interceptor.CommandCounterInterceptor.execute(CommandCounterInterceptor.java:35)
at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:33)
at org.camunda.bpm.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:179)
at org.camunda.bpm.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:175)
at com.vodafone.solstice.care.commons.camunda.config.TaskServiceWrapper.complete(TaskServiceWrapper.java:105)
at com.vodafone.solstice.care.commons.adapters.camunda.UserTaskServiceProvider.lambda$completeTask$2(UserTaskServiceProvider.java:131)
at com.vodafone.solstice.care.commons.adapters.camunda.UserTaskServiceProvider.lambda$execute$6(UserTaskServiceProvider.java:222)
at org.springframework.transaction.support.TransactionOperations.lambda$executeWithoutResult$0(TransactionOperations.java:68)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
at org.springframework.transaction.support.TransactionOperations.executeWithoutResult(TransactionOperations.java:67)
at com.vodafone.solstice.care.commons.adapters.camunda.UserTaskServiceProvider.execute(UserTaskServiceProvider.java:222)
at com.vodafone.solstice.care.commons.adapters.camunda.UserTaskServiceProvider.completeTask(UserTaskServiceProvider.java:117)
at com.vodafone.solstice.care.workflows.core.billdispute.integration.BillDisputeProcessStepDefinitions.ticketIsManuallyHandled(BillDisputeProcessStepDefinitions.java:182)
at 
...