Scheduled messages that included message center as part of their payloads may not have been delivered if they were created between approximately 3:25 PM US Pacific time on 19 March and 3:08 PM on 21 March. By 3:40 PM, all remaining scheduled messages created during this period were repaired so they would be able to be delivered successfully. This defect was introduced as part of major changes to our scheduling system, which will improve its queueing services and make it much more flexible and reliable in the future. Future changes to this system should be easier to test and less likely to cause unexpected errors. We apologize for any inconvenience.