This is indeed WAD. It's an annoying situation yes, but at least you should have a claim on the duchy so the new ruler isn't really out of the woods just yet!
It seems to be a bad case of bad luck to be frank, and as much as I feel for you I can't pass it on and classify it as a bug.
It seems to be a bad case of bad luck to be frank, and as much as I feel for you I can't pass it on and classify it as a bug.