title: Wso2 bps process hangs without reason
body: <p>I have simple bpl process with 3 invokes in loop. One of instances hang without any visible reason. So process is in active state but it is not executing any longer. Last logged activity is call to invoke. I search database and find out that both request and response are present in table ode_message and they looks correctly. But output variable from invoke in table ode_xml_data is not filled. There is no logs in bps from time when message arrived. Is any way to find out what happen wrong?</p>
  
  <p>I'm try to use Wso2 BPS 2.1.2</p>