Items Missing when creating Purchase Order with Dropship Default Values

I am trying to create a Dropship Purchase Order via SuiteScript 2. I am able to create the Purchase order object with the correct Drop ship data (customer, Sales order, Dropship form) however I get the following error when saving

"You must enter at least one line item for this transaction.".

I can manually create the drop ship from the Sales Order and the items add fine. I am using Netsuite OneWorld.

Below is the code I'm using

var purchaseOrder = record.create({
                type: record.Type.PURCHASE_ORDER,
                isDynamic: true,
                defaultValues: {
                    soid: 4427821,
                    dropship: true,
                    subsidiary: 9,
                    custid: 666,
                    entity: 322
                }
});
purchaseOrder.setValue({
    fieldId: "employee",
    value: 3
});
    
log.debug("Item Count", purchaseOrder.getLineCount("item"));
log.debug("Entity", purchaseOrder.getText("entity"));
log.debug("Customer", purchaseOrder.getText("shipto"));
log.debug("Sales Order", purchaseOrder.getText("createdfrom"));
log.debug("Form", purchaseOrder.getText("customform"));
log.debug("Subsidiary", purchaseOrder.getText("subsidiary"));
    
purchaseOrder.save();

Here some screengrabs as well

Sales Order

Manual Drop Ship PO

Script Logs

I have existing scripts that create standalone POs, so I have some idea of the process required here. Is there a step I'm missing for Dropships specifically? I found this thread in which Will Charbonneau said this should be all you need Netsuite: How to link Purchase Order to Sales Order. I've tried Their code with my IDs, and it results in the same error.

Solution

So in case anyone is still having trouble with this, I figured it out.

var purchaseOrder = record.create({
            type: record.Type.PURCHASE_ORDER,
            isDynamic: true,
            defaultValues: {
                customform: 180, //dropship custom form
                soid: 4820583, //Sales order internalID
                shipgroup: 1, //from 'dropship' button url via UI
                dropship: true, //from 'dropship' button url via the UI
                custid: 666, //customer InternalID
                entity: 322, //vendor InternalID
                poentity: 322 //vendor InternalID
            }
        });
var poid = purchaseOrder.save();

I don't know why half of these fields are not documented anywhere (defaultvalues or the schema) but this auto populates the items and customer details just like it would via the UI.