The new query engine will handle all criteria in the query, but currently there is no handling of any CONTAINS clauses. Thus, when a query that uses CONTAINS is executed, it fails with a nasty exception.
The plan is that users will be able to create full-text indexes for the query engine to efficiently and quickly handle their queries CONTAINS clauses. However, when no index is applicable the fallback is for the query engine to simply evaluate the clauses. This is what needs to be fixed.