The collapse.section user preference causes missing fields

User Preferences collapse.section.<form_section_sys_id> causes missing fields in task forms.

This issue is difficult to reproduce.

If a user preference like collapse.section.3ed906446f94d10039be93d31c3ee464 is present in the sys_user_preference table with value of true, the form section with sys_id=3ed906446f94d10039be93d31c3ee464 is collapsed when accessing the relative task form.

This is expected behavior only if the collapse.section user preference has been created intentionally.

1. Determine the affected users.
2. Remove all their user preferences associated with collapse.section.<sys_id>.
3. Clear the instance cache (/cache.do).