Unthrown errors using PHP SDK (API v2)

We've noticed that in some cases the new API will fail to insert a record (for example) but not throw an error (ZCRMException) when there is a problem with one part of the request. For example, if we try to set the Lead Owner to the user's name instead of their User ID, the entire insert fails silently:

this snippet works ...

$record->setFieldValue("First_Name","John");
$record->setFieldValue("Last_Name","Doe");
$record->setFieldValue("Email","john@doe.com");
$record->setFieldValue("Owner","1231231231231231231");

this snippet does NOT work (no error returned) ...

$record->setFieldValue("First_Name","John");
$record->setFieldValue("Last_Name","Doe");
$record->setFieldValue("Email","john@doe.com");
$record->setFieldValue("Owner","Jane Doe");

(Simply removing the owner setFieldValue also works.)

We can listen for the success response to determine if the insert failed, but it would be helpful if either (1) valid field values were added and/or (2) an error (e.g., "Invalid Field Value for Owner") was returned.

Finally, a related question: are we supposed to set the record owner using setFieldValue? What is the function of the setOwner method in the ZCRMRecord class?

Thanks.