Seaquel
SQL Server error code

SQL Server error 6978

SQL Server raises error 6978 at severity 16, which marks a problem with the query or data that you can correct.

Invalid item type for list type '%s'. The item type of a list may not itself be a list, and types derived from ID may not be used as item types in this release.
Msg6978
Severity16
Group6000–6999

Source: Database Engine events and errors