Fieldset of previous profile disappears

I'm trying to group some Profile 2 fields into a fieldset, using Drupal core 7.26, Profile2 7.x-1.3, and Fieldgroup 7.x-1.3. Reading the related issues in the Fieldgroup issue queue, it sounds as though Fieldgroup should work with profiles.

First I confirmed that Fieldgroup is working fine with node types (screenshots #1 and #2).

I then edited the "Main" profile, adding a text field, and nesting that inside of a "Fieldset" field group (screenshots #3 and #4). On the user registration form, the new field and its enclosing fieldset are displayed properly (screenshot #5).

I then created a custom profile, a field group (careful to use a different machine name from the previous field group), and fieldset (screenshots #6 and #7). On the user registration form, the new field and its fieldset are displayed, but the previous one has disappeared (screenshot #8), even though no changes were made to the "Main" profile or any of its fields. Any ideas what is going wrong?