iTunes duplicates calendar events when syncing with Outlook

I'm struggling to find a way to stop iTunes from duplicating my calendar events while syncing with iPhone.
I upgraded to a new Windows 10 PC recently and tried to sync Outlook 2016 (I only need calendar from there) with my iPhone 7. However, iTunes doesn't seem to work properly on this new hardware or software configuration.
Is there still a way to fix iTunes as I don't like using iCloud for syncing.

P.S. I've tried reinstalling iTunes, no luck.