FieldsetGroup does not work

[kaz]

I have a template with settings. The data are created in FieldsetGroup's. When I select a FieldsetGroup the cursor changes to a hand and I may open the group.

I had to remove a group from the template. I removed the group via the icon, and confirmed the warnings. On the page which uses the template everything looks right. But unfortunately the other groups can't be opened now. I click, nothing happens.

So I took the group back into the template (although I don't need the parts), but unfortunately the FieldsetGroup's remain dead. What could be the reason for this?