If you are a user of the adds-changes (so-called "incremental") dumps, read on.
All dumps use database servers in our eqiad data center. For the past month, the wiki projects have used primary database masters out of our codfw data center; on one of these days, a number of revisions did not replicate properly to eqiad for about 50 minutes. This was not discovered until we switched back to using the database servers in eqiad as primary masters.
The date that replication was broken was September 13th. Because dumps use eqiad database servers, the adds-changes dumps published on that date are also missing that data.
We suggest that if you are using adds-changes dumps for a local mirror, you import the next regular run of xml/sql dumps, starting on Oct 20th (for current revisons only) or Nov 1st (for full history), which should contain the missing revisions.
For more information on this incident, you may follow: https://phabricator.wikimedia.org/T206743
Ariel