Assume that you have an Always On Availability Group (AG) in an instance of Microsoft SQL Server 2016 or 2017. When you back up a secondary replica that is running under asynchronous-commit mode, the backup operation may fail occasionally. Additionally, you may receive the following error message:
Error: 9003, Severity: 20, State: 1.
The log scan number (nnn:nnn:nnn) passed to log scan in database 'dbname' is not valid. This error may indicate data corruption or that the log file (.ldf) does not match the data file (.mdf). If this error occurred during replication, re-create the publication. Otherwise, restore from backup if the problem results in a failure during startup.
This problem is fixed in the following updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.