See attached drawing:
the top transition is taken first if it appears first in xml.
the error propagates to the boundary which is interrupting and destroys the scope (hence both concurrent executions created at the parallel split are destroyed.
(the transition on the boundary destroys the scope exection)
HOWEVER: sine we are still in the foreach-loop at the parallel split, the second concurrent execution continues to the usertask and created the task in db, which leads to an exception at commit-time, since the foreign key constrain on Task->Execution is now violated.