Duplicate names glitch?

Please tell me if I have a setting I need to change to prevent this, but in the seating plan when I move a student from point A to point B in the plan a duplicate student appears in the spot I moved the student from. If I leave the seating plan screen and come back, the duplicate disappears. 

Hi ,

You can move the students normally , when you get its duplicated just enter the gradebook / again to the seating plan
and duplicates are gone.
Anyway next week (Wednesday) a new version of iDoceo will be available in the AppStore with this problem 
already solved.
This link will download the new version.
apps.apple.com/gb/app/idoceo-planner-and-gradebook/id477120941

Best
Karla