Just a forewarning, ODBC connections tend to have limited functionality.
I don't know much but have you tried alternatives like
WHERE (`Custom_SQL_Query`.`boolean_field` = 'TRUE')
WHERE (`Custom_SQL_Query`.`boolean_field` IS TRUE)
Or what about an explicit data type cast or convert? I don't know what syntax your SQL would be but here's an example of what I mean: CAST and CONVERT (Transact-SQL)