have to raise tasker before each event or it fails

I am using tasker on a Chromebook to watch for a file open, then send a page_down keypress event to the foreground (target) app.  It works perfectly...one time.  All subsequent file open events generate correct log entries in tasker.  The file open event is noticed by tasker, and it correctly fires the keyboard input task; however, it does not result in a page_down action in the target app.  If I bring tasker to the foreground momentarily, then the cycle works successfully again one time.  Minimizing and restoring the target app does not work.  Focusing an unrelated app does not work.  The only thing that works is putting tasker in the foreground then selecting the target app.  Then it works one time.