There is a "Timeout" setting (in seconds) defined with each scheduled task. When entered it allows to automatically restart long running scheduled tasks, which in fact may be just hang up and haven't reported their status due that.
Right now it happens automatically and in of low timeout value we maybe restarting scheduled task even while it is running and this way creating possibility where 2 scheduled tasks will run in parallel.
I'm proposing to raise a notice each time scheduled task is reset by Timeout setting. This notice will go into "System Log" section and later developers can review it and confirm that such problem doesn't happen.