Published dates of sermons changed when updating plugin to version 2.15.12

We did the automatic update in WordPress to version 2.15.12 on Dec. 17th (along with many other plugins), and just realized all the Published dates for the sermons changed to Dec. 17th, 2018. The sermons appear to be in the correct order on the archive page, but on the home page (https://www.christchurchnashville.org/) at the bottom “Recent Sermons”, the list of recent sermons jumps to posts from 2012 (after the one published after the update occurred).

We can probably revert the site to a backup before the 17th to restore the correct publishing dates, but we will have to reload in any new content. Any ideas as to why this error happened?

The page I need help with: [log in to see the link]