Total sync again after reinstall?

Hi there,
I am a Nextcloud user for a while and today I decided to uninstall my Mac desktop version (2.5.3) to update the new version (2.6.1). My setup is : a folder on my Mac to be sync with my NAS (through Ethernet). After I launched the new version, Nextcloud has scanned all my folders modifications and is now resynchronizing everything (over 50 Gb, so about xx hours).
Why ? Nothing has changed (except 3 or 4 files), no change in computer/NAS time… I don’t understand… Thank you for your help.