Field groups in Web Content Structures become Field Sets after Import or Modification

Issue

When a web content structure containing a field group is imported via a LAR or JSON file, the field group is converted into an uneditable, referenced field set.
This issue also occurs when modifying and saving an existing structure that contains a field group.
As a result, the fields within the group can no longer be edited, and the new field set does not appear in the list of available field sets for management.

This issue is caused by a product defect where the fieldset's ddmStructureId property is incorrectly set to "null" instead of an empty string.
The resolution involves two steps: applying a hotfix to prevent future occurrences and running a script to fix existing broken structures:
1. Apply Hotfix
  - To prevent this issue from occurring with new or modified structures, request a hotfix including LPD-61671.
2. Fix current structures
  - For structures that are already affected, the attached Groovy script can be run from the Control Panel's Script Console to correct them.
  - This script iterates through the structures and fixes the incorrect fieldset definitions. You will need to update the companyId variable in the script to match your instance.
  - Important: Before running the script, ensure you have a database backup.
Kindly contact support if the issue persist.