Thanks for the review. What I'd like for you to do is this:
1. Next time it does not drop as expected, tap the ? button at the top, and send in a quiz report. You do not need to do that for *all* of them, just 2-3.
2. You can respond here letting me know you've done that, as I see forum replies more easily than than quiz reports (which I tend to do in batches)
Also, are you currently using the holiday system for the schedules?