Signal is not thrown to event sub process

Hello,
in the example the signal X should be thrown and the flow continue in the event sub process, but it does not. I know that the flow in the main process is interrupted because in the event sub process it is an interrupting signal start event. Though the flow should be in the event sub process at the user task “sub”.
Any ideas why the behaviour is like that?
Thank you very much!


Signal Event Subprocess.bpmn (7.7 KB)

i can understand how this happens, I’d need to check it if complies with the BPMN standard. It may very well be the intended implementation.