In a compact binary newsgroup, I tried to "undelete headers" in the "advanced" context menu, but nothing happened. I then tried checking "Deleted" in Properties/General under "Tracking expired/purged headers." Then I downloaded some more headers, applied "delete headers and replies", and then tried to "undelete headers" again. However, the headers still did not return to the newsgroup view window; again nothing happened.
This is not consistent with the operation of this command in NewsPro, where it worked fine.