Hello Bhavesh,
it is hard to say what the reason behind an action not being triggered might be. Since EHSM 2.0 SP02 (released mid 2012) a lot of corrections have been performed. My first suggestion would therefore evaluate if an update to the current SP6 is possible.
In order to analyze the error why a process is not triggered the corresponding error needs to be analyzed. This may best be done on a development system, since changing a background WF task to a foreground user task in order to debug it may be something you only want to have in development rather than production.
Regards
Joachim