Shipment Processing Workflow Lab error?

Hello,

I ran into an error following the current lab:

Shipment Processing Workflow

On the first loop block after the initial trigger (callShippingService), there appears an error saying callShippingService_lambda is undefined:
image

The thing is that I've also imported the complete workflow with the JSON provided at the end of the lab, and the same code does work, it has no problem with callShippingService_lambda. I've even tried to copy the code from this working workflow to the one failing, and it says the same.

Even though it says undefined, does it still run successfully?

It fails to run.