I’ve upgraded the leafnode package to version 1.10.7 in order to get Xref: headers in the XOVER responses. There was a bug since 1.9.50 that inadvertently caused Xref: to be dropped out when creating the overview database.
If you think it is no more deja vu when reading an article again, this could be the reason. At least nn depends exclusively on overview data for the Xref: header contents when determining cross-posts you have already read.