Sorry in advance if this is too much detail, but you seem to be interested in the nuance here. "Unfortunately." here is a sentence fragment. It's idiomatic (co

Sorry in advance if this is too much detail, but you seem to be interested in the nuance here. "Unfortunately." here is a sentence fragment. It's idiomatic (conversational + informal) English to modify a preceding sentence with a sentence fragment. ("We could have some iced tea. Or lemonade.") There are cases where a sentence fragment can be used to introduce a sentence ("Delicious. I ate the whole thing.") but this is never an adverb (you can say "Unbelievable. You've done it again" but not "Unbelievably. You've done it again"). If one were trying to write "Unfortunately, there has been an error" with a long pause, you would write "Unfortunately... there has been an error", never "Unfortunately. There has been an error." The latter looks like a typo. That's why (as a native speaker/reader of American English) I don't see any possibility of interpreting the text the way you're describing. Hope that helps!