After reactivating Events the Display locations as "Pages" changes to "Posts." When you have already set the value to Pages it reverts back to post. This is quite annoying when you do not know why the events do not show, but instead receive a 404 page not found.
Is there away that these values can survive a deactivation?
http://wordpress.org/extend/plugins/events-manager/
this should only happen once, when you upgrade from v4 to 5 (to give the same effect as before). Unless your dbem_version value in your wp-admin/options.php page never gets updated to 5.x, it can't be an EM issue, could you try doing this without other plugins enabled?
Forgot, some of those plugin values reside in WP tables and not in the plugin even if the plugin is completely deleted.