An alternate way to remove the user other than using the WebUI.

You may run the CLI command below to remove the user. 

echo "delete from users where username='<Username>'" | su - postgres -c "psql -d dsweb" 

For example, if you are trying to delete the user 'helpdesk1', you would run the following command: 

echo "delete from users where username='helpdesk1'" | su - postgres -c "psql -d dsweb"