goto course >> admin >> stats >> export csv and check who has finished the course, after that, you can delete their records manually from the database. it won't delete permanently. there will remain garbage value.
you cant clean assignment. this will remain forever. yes it takes time because it has a lot of queries and also performs many checks to verify the complete records. if we remove those then it will give false results.
THanks, Also I just noticed that the new students submitting does not appear on evaluation complete. How do i fix this. Its like the list stops and new peeps are not added.
This could be a third party plugin which is causing code conflicts.
Please deactivate all installed 3rd party plugins.
Delete browsers cache
Re-save permalinks.
If it does not work only then share your wp-admin URL and credentials with course specific page url in a private reply so that I can look into this matter.