You may receive time-out errors when you use SQL Server 2016 AlwaysOn Availability Groups. Additionally, you receive error messages on a sync secondary that resemble the following in the SQL Server error log:
Always On Availability Groups transport has detected a missing log block for availability database "database_name". LSN of last applied log block is (LSN_ID). Log scan will be restarted to fix the issue. This is an informational message only. No user action is required.