Working on critical issue involving undelivered tweets 2 years ago

We are actively investigating a critical issue whereby users’ tweets are not being delivered to all of those users’ followers. This issue particularly affects users with a very large number of followers.

Update (6:37p): We have identified several contributing issues and have made improvements. Some tweets continue to be delayed or undelivered, and we are continuing to investigate the issue.

Update (12:00a): We have made further improvements and have substantially corrected the fault. We are monitoring for any further instances of the issue.