When we were having problems getting all of the Advance Notices to generate/email every day, I was running reports daily in order to confirm which notice scripts were running correctly. While reviewing the reports I noticed that there were many patron accounts that were receiving multiple "Advance Notice of Item Due" or "Item Due reminders" notices on the same day. And I wondered if that was contributing to the problems we were having.
The recommendation for these notice Preferences is to always check the Digest option when selecting these notices types. That way patrons will only receive one "pre-overdue" email notice per day, instead of several.
If you are working in a patron record and you see that they have one of these options selected, please ensure/confirm that the checkbox in the "Digests only?" column is selected as well.