Every website I use with this plugin seems to have the same problem.
SEO sitemap breaks if Sermon Manager is Active.
When it is active, the Sermons permalink does not work, it will return 404 on anything under that slug.
After trying to figure out what happened, I realized the only thing that has changed on the sites was upgrading from PHP 5.6 to 7.
Has this been tested on PHP 7? I do not wish to rollback to 5.6 to find out.