Copy Value from Task to Contact Function Says Successful Update Did Not Happen

I have a function that tasks a taskid as a parameter, reads the Who_Id from the task to get the contact it's linked to, then populates the Sales Owner (custom user lookup field on Contact). Testing the function indicates success, yet the field is not update when you go back to the contact.

Pretty straightforward Deluge code:

taskDetails = zoho.crm.getRecordById("Tasks",taskId);

contactId = taskDetails.get("Who_Id").get("Id");

taskownerId = taskDetails.get("Owner").get("Id");

mp = Map();

mp.put("Sales_Owner",taskownerId);

update = zoho.crm.updateRecord("Contacts",contactId,mp);

info update;

Any thoughts as to why this is not working? I dbl-checked that the Sales Owner field has permissions.

I've also tried

mp.put("Sales_Owner",taskDetails.get("Owner"));

and that was same, says successful but nothing updated.

Thanks