Saved search alerts not always working

Hello,

I've created several saved search alerts based on the following criteria: subsidiary, territory, campaign response category, campaign response date (as today), created date (using a past date so that all leads that were updated gets picked up). I've checked off "Send email alerts when records are created/updated", added to the recipient list, on Recipients from Results, i chose "Account Manager" checked send on update, customized the message and used single-record results with indicated fields.

I asked my IS department, and they said that I must add created date and subsidiary to the criteria for the alert to work - I did that even though I never had to use that criteria before. The alerts don't always work - however when I run the saved search, the lead will show up - meaning it should have been picked up and sent off via email.