Guided Process saving custom object gives error

Summary:

Hi all,

We are making a Visual Builder application where we have a custom object, with 3 child objects (one-many relation).
I have now tried making a guided process page with the template where in each step users can fill in the separate objects, and at the end the action would save each object by calling the create action chains of each object. However this gives the following errors:

I think the issue is that when going to the next step, the gotoNextStepActionChain does a navigate to page action to go to the next step on the same page, but i don't know if the page variables that hold the data for the custom objects are transferred like this. I added a console.log action to call the page variables and they are all null.