I've only ever had this, or something like it, happen once, and it was in DA 1.7ish. I know that bug was fixed, as it was apparently tied to the Xeno Ethics bug that allowed you to zero out your debt, but I wasn't aware anything similar ever existed, or that it still does, in DL.
And for what little it's worth, I was only about 537 million in debt-I could still (sort of, my memory of the game is a bit fuzzy nowadays) see how screwed I was. Yours may in fact be another order of magnitude or more beyond that, if you can't actually tell how bad it is.