Help deleting duplicate enteries in splanner on S6

pedigree

Hi
I have spent hours on Google trying to come up with a solution for this.
Samsung S6
using S Planner as my calendar.
Syncing with MS outlook using smart switch.

Problem every time I sync the items in spanner are duplicating - result multiple entries for the same event.

I cant find a way to delete the duplicates other that individually deleting each entry.
Another option is to delete the complete calendar, I have tried this through application manager but it wont stop or delete for me.
All help appreciated.
Thanks
Pedigree

Matesta

Take a backup of your Outlook calendar first (in case Smart Switch decides delete the events from Outlook to keep it in sync with the phone)
To delete all calendar events:
Settings -> Device -> Applications -> Application manager -> Calendar -> Storage -> Clear Data.
To solve the issue of duplicated calendar entries I recommend using AkrutoSync.

pedigree

Thank you for the reply, I have followed your instructions
Settings -> Applications -> Application manager -> S Planner -> Storage -> Clear Data and I re-started the phone.
The calendar hasn't cleared, now it is saying data of 104kb it was 330kb so I repeated the process. Re-started the phone result still not cleared the amount of data is still at 104kb.
Repeated again, result 124kb data 4kb cache?
I had tried this yesterday a few times but it didn't ever clear the calendar. I am not syncing with any cloud (that I am aware of).

pedigree

After multiple attempts to delete the data through the application manager, the calendar is still populated. I can only conclude the calendar is syncing with something could it be my Samsung account or my Google account. Can anyone help in this area.
Tried deleting with Flight mode on but it made no difference.
Thanks