Activity hangs on start point

Hi everybody!
We have such a problem: we have a process (Categorization.Result.Notify) with a parallel gateway and 3 flows going from it. Sometimes it is executed normal, but sometimes, the second activity from the left flow (Activity_0x9ka8y) is starting and hanging at the start point in schema internal-AMQ forever. After 10 minutes (our lock-time-in-milles) other execution of hanging activity starts, it finishes correctly, but in the joining endpoint process fails, because of not finished hanging activity:

org.camunda.bpm.engine.ProcessEngineException: ENGINE-03083 Exception while executing Batch Database Operations with message ’

Error flushing statements. Cause: org.apache.ibatis.executor.BatchExecutorException: org.camunda.bpm.engine.impl.persistence.entity.ExecutionEntity.deleteExecution (batch index #1) failed. Cause: java.sql.BatchUpdateException: The DELETE statement conflicted with the SAME TABLE REFERENCE constraint “ACT_FK_EXE_PROCINST”. The conflict occurred in database “Activiti”, table “App.ACT_RU_EXECUTION”, column ‘PROC_INST_ID_’.

Why is the activity can be hanging?

Categorization.Result.Notify.bpmn (32.2 KB)
internal-AMQ.bpmn (17.1 KB)