Custom alert is not sending email to all the learners

@Debbie Tatu-Oracle

Summary:

We have a custom alert which send email notification to learner when we create required learning initiative/assignment.

This alert is working fine when we have 700/800 learner.

But it is not working when we are creating initiative for 3000 or 4000 learner. Its skipping 400 -1k learners for the email alert. Although we can see the course got assigned to them

PS: there is no message limitation

@Debbie Tatu-Oracle @Jamie Rancourt-Oracle @Anders Northeved-Oracle

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):