I know the stack crew is messing with the close experience but I haven't heard anything about closing as dupe no longer offering a link to the dupe. Please let me know what's going on when I see this:
Yes: this is definitely an issue, and No: it does not seem to be related to the duplicate questions not having any answers (an issue that was resolved months ago).
It is a new issue having to do with a specific scenario where the post owner accepts duplicate suggestions and self-closes as duplicate. While it is definitely occurring, I cannot repro locally.
I am adding some fixes to related issues here that may end up taking care of it, a fix for the "duplicate comments" not being deleted, and additional logging to aid in further debugging should the issue continue. (Changes have not yet been merged, I will update when that has happened, but I wanted to update here that this is being looked at).
-- Yaakov Ellis