Nested Metabox Data is not shown in GB Element

Hi there, I am using Metabox for custom post types and custom fields. When adding them to a GB element, the nested data isn’t coming through. One Level works normally, but e.g. fields within groups cannot be accessed.

I previously used Advanced Custom Fields and there, the groups were working. (group_subfield)

Is this a mistake on my end or is this functionality not there?