Problem with multi-valued fields in toggleable forms

There's a problem with using more than one toggleable form in a tab – say you have two forms, both containing multi-valued fields. The Add button on the field in the first form will work, but the Add button in the second form will do nothing.

To reproduce:

• Create a tab and two form layouts
• Add a multi-valued field to each form layout
• Add the form layouts as toggleable forms to the tab
• In the tab, add values to the first form, then try to add values to the second form without previously editing the first form