In addition to this issue.
If edit form on some profile category then validation goes throught main category. And if it have unvalid elements - show error, but it does not matter because we not edit main category.
Explain on example.
- We have enabled "User edit template" ctools page and Simplenews module.
- On profile page we have 2 tabs: Main profile, Newsletter.
- When edit user Simplenews subscriptions we have error about unfilled some fields in profile (for example "Birthday"). But we don't edit profile at all! We only need edit subscriptions which are on separate tab and category.