Signal not getting invoked externally through rest API when it is in Error Scenario

We have a process with some "Catching Signal Intermediate Events", a "Throwing Error End Event" and an "Event Sub-Process" where the first step is an "Error Start Event". Please find the process model attached to this email (picture -> myerrorprocess_model.png and source code -> org.jbpm.myerrorprocess.v1.0.bpmn2).

Once a process instance is created, the workflow is awaiting in the "Signal1" catching signal intermediate event. Then we invoke a signal with the value "signal1" and it moves forward. According to the process definition, the workflow should wait in the step "Sub-signal1" of the event sub-process but it moves forward and waits in the "Script2" task. Finally we are not able to invoke the signal for moving forward. Please find the workflow final status attached to this email (current_worlflow_status.png).