It happened to me also, luckily i have a manual save during the quest itself so i rolled it back once i realised. To me the completed quest seems to get deleted once an autosave is loaded at any time after completion if said quest, which in turn stops the romance dialogue. One this occur it effects every save apart from any done during or before the taken for granted quest. I also did the east anglia arc as my 3rd alliance. I'm holding off completing the taken for granted quest and continuing the story until this is fixed.
Any updates in any upcoming patch which may resolve this?