Causes white screens, support nonexistent

This is very disappointing. The plugin promises to do exactly what I was looking for. However, upon updating jobs that have expired, WP-admin goes blank (white screen) and nothing is processed.

Debugging provided the following error:
Notice: add_submenu_page was called incorrectly. The seventh parameter passed to add_submenu_page() should be an integer representing menu position. Please see Debugging in WordPress for more information. (This message was added in version 5.3.0.) in /website.com/wp-includes/functions.php on line 5225

After 2 weeks, still no reply whatsoever to my support thread.