Alarm Notification Pipelines: events missing


I'd like to know if anyone among you thinks that occasionally some alarms (purely random) are not being notified through the "alarm notification pipelines."

I am using a pipeline to send email notifications to certain groups, and the system has been functioning well so far. However, today an operator showed me that he received an SMS (the SMS are sent from our old application, which will be completely replaced by IGNITION), but he did not receive the email. Most of the other notifications are working fine!