Before I could customize and uncheck the multiple task option, some of my customers made appointments for same slot; as result one appointment  was confirmed and the other  stayed as pending and even I deleted them, when I check the timetable report I still see the black cells as you can see in the picture. I've tried to search for duplicates in databases in phpMyadmin but everything seem to be ok there.   How can I get rid of those ghost appointments? https://ibb.co/b7RKkrH