Seaquel
SQL Server error code

SQL Server error 2515

SQL Server raises error 2515 at severity 16, which marks a problem with the query or data that you can correct.

The page %S_PGID, object ID %d, index ID %d, partition ID %I64d, allocation unit ID %I64d (type %.*ls) has been modified, but is not marked as modified in the differential backup bitmap.
Msg2515
NameDBCC_DIFF_MAP_OUT_OF_SYNC
Severity16
Group2000–2999

What it means

The page specified has a log sequence number (LSN) that is higher than the differential reference LSN in the BackupManager of the database, or the differential base LSN in the file control block of the file, whichever is more recent. However, the page is not marked as changed in the differential backup bitmap.

Source: Database Engine events and errors