I am having the same problem. On my forum index page, the freshness has been wrong for a week since the last upgrade to bbpress 2.6.2. (Never a problem before then.) I have only one index page, then topic pages (where the freshness is correct). I did have WP Supercache on the site, but removed it 4 days ago, including all the extra steps to remove any remaining cache files outside the plugin. The freshness is still incorrect and lags by several days, even with clearing the browser cache, or trying an in-private browsing page. I have also been in touch with my host (Siteground) and they cannot find an issue. They asked me to deactivate all my plugins – which I did, on a staging site – and still, no, it seems to be just the bbpress upgrade. Help! Any more suggestions?