I did a crude patch for MySql As Follows:

public static int Save(T record)
{
var sqlToExecute = "";

using (var Db = GetConnection())
{

try
{
var insertSQL = Db.ToInsertStatement(record);
var updateSQL = Db.ToUpdateStatement(record);

// strip out the UPDATE 'tablename' SET ....
updateSQL = updateSQL.Replace(Db.GetQuotedTableName<T>(), "");
updateSQL = updateSQL.Replace(" SET", "");

// remove trailing WHERE <PK=Id>...
updateSQL = updateSQL.Substring(0, updateSQL.IndexOf(" WHERE `"));

//lastly something weird with nulls = '{}'
sqlToExecute = (insertSQL + " ON DUPLICATE KEY " + updateSQL).Replace("'{}'", "NULL");

Db.ExecuteSql(sqlToExecute);

return 1;
}
catch (Exception e)
{

Log.Error(0, $"Error saving record, sql={sqlToExecute}", e);

return -1;

}
}
}