Seaquel
SQL Server error code

SQL Server error 6213

SQL Server raises error 6213 at severity 16, which marks a problem with the query or data that you can correct.

%s ASSEMBLY failed because method "%.*ls" on type "%.*ls" in %.*ls assembly "%.*ls" has a synchronized attribute. Explicit synchronization is not allowed in %.*ls assemblies.
Msg6213
Severity16
Group6000–6999

Source: Database Engine events and errors