Thank you for fixing this so quickly!
Duplication detection is now working – I should have really have noticed that checkbox.
I’ve resolved the scheduling issues by following the instructions above to disable cron, and adding this line to the crontab file:
0,30 * * * * wget -q -O – https://<site-name.com>/wp-cron.php?doing_wp_cron >/dev/null 2>&1
Thanks again!