Calendar sync between Outlook and Samsung Galaxy S7

[GD61]

Hi,
Since several weeks, this sync has a strange behavior : it deletes and then creates again all the official days off, all the week numbers...
So the sync is quite long!
How to prevent the sync from doing this strange behavior. Previously, it was working fine.
Thanks for help

[GD61]

and in the Deleted Items of Outlook I receive a lot of emails: one for each Day Off, one for each week number....