The question is on your precedence constraints that enter the level 3 task did you change the default of ANDing constraints to ORing, since this is what you want. If you did not then the execution is as expected since only one of the 2 constraints entering level 3 is "executing". Try changing the constraints to the level 3 task to OR and see if you get the behaviour you want.
HTH,
Matt
This posting is provided "AS IS" with no warranties, and confers no rights.