The opaque_transform hint is related to datatype transformations of certain types like object types when the operations take place in the database and is also used for an insert-as-remote-select operation on a remote database.
The hint is not intended to interfere with an execution plan.
The following events can be set on the local database to turn the hint off or on:
alter session set events '22825 trace name context off';
alter session set events '22825 trace name context forever, level 1' ;