max size for forms using multistep or groups

I’m using the Pro version of this plugin and I’m building a very large form using multistep and a lot of groups.
In this form in the first step (choose “nee” in the first field) multistep stops working after I have added the fields for “Aanvullende informatie complex”. The buttons for next step aren’t located anymore at the bottom but are floating on the right of these added fields.
Is there a maximum size of the form or the number of fields or groups that I can add?

The page I need help with: [log in to see the link]