‘SOLVED’ is a bit overselling it. If you have EXTRA REGISTY SETTINGS in a Group Policy what you have settings that were set in an old .ADMX template. In other words they are orphaned. You likely added in new templates (like the Windows 10 templates) and the new template does not support your old setting so GPMC shows it like:
The only way to resolve this is to rebuild the policy from scratch. This is time consuming and annoying. Microsoft is aware of the issue and if you are an MS Partner you can add your comments to my thread with them here.