Duplicated all entries when updating sources

Hello,

Before, my tv shows were on a hard drive, and now their are on a Synology NAS.

Scanning all my tv shows was very long when their were on my hard drive so i decided to follow a guide to update kodi database and change the path of all my episodes.
It is working well, i can watch my tv shows from my NAS.

But when I decided to update my sources to the new path to my NAS, (i tried on a little folder for testing, all episodes has been re-scanning and all is duplicated …).

I dont want to rescan those i already have.
Is there a way to avoid that ?
In the database can we say this folder has been already scan, so dont re-do it ?

Sorry for my poor english,

Regards,

Abra.