I have come across a recurring issue when going into a previously approved form and editing one of the form labels. The form label displays the old label on a preview and on a page, but when you go back to the edit pane it has the correct new label. I have had to delete the field from the form entirely, re-add it correctly and then re-approve. It now turns out the same thing happens if you clone an existing form to a new draft, edit a label and approve.
Any help is appreciated as this is quite an inconvenience when editing fields with complex rules applied.