Can one knowledgable in Swedish comment on the discussion? We have dramatic change from passive (Swedish) to a noun (English) in the translation. For me even: The cinnamon buns were screwed up. sounds closer to the Swedish version (if I understand at all what this Swedish sentence means - somebody did something to the cinnamon buns, I assume, but I am not clear what it was that was done to them, there is nothing in English translation that clarifies what was done to the buns).
I take it as "the cinnamon buns disappointed" in some way. Maybe they were unpalatable or not popular for whatever reason. I don't think either the English or the Swedish implies that someone did something to the cinnamon buns.
I don't really get what you meant. Doesn't The cinnamon buns were failed. just describe the state of the cinnamon buns in an objective manner?
He is saying the English "were failed" implies an action performed on the subject (the cinnamon buns). You could also say "the cinnamon buns failed", but that's a different tense: "Kanelbullarna misslyckades." So I think we either have to say "were a failure", "were failures", or "were unsuccessful" in English.