Hello, I recently ran into the same issue so many others have had regarding the timestamp on lastmod being off by many hours.
What I did, since most sitemaps only have the y-m-d and not TIME. I made it to where the sitemap.xml only contained y-m-d.
To do this you will need to edit class.xml-creator.inc.php under the pages folder.
Simply edit line 131 to 'LASTMOD'=>date('Y-m-d') and line 576 to $WlMIEENwbMQ = gmdate('Y-m-d',$WlMIEENwbMQ);
Save and re-run cron.
Guest