Sync slower and slower

[tra_ma_sea_rider]

Hi all

I encounter a problem using FreeFileSync, (Last version - 10.14).
I'm syncing my computer on to my USB hard drive (FAT 32 / 64 Go Kingstom) once a week with about 1 to 3 Go of data and it takes me about half a day each time.
It looks like it stops after every single file it copys, wait for a few seconds and start a new one.
When i do the first sync ever, it goes at a relative normal speed but when I sync on the next time, it's just a pain.

I've tested my USB stick, looks normal when I directly copy files on it.
I've activated the Backgroung priority on FFS and try to desactivate the
If changed the relative adress of my usb stick to the device windows default letter
I've defragment my USB stick

Would you have suggestions ?
Do you think it can come from my usb stick even if it works well on manual copy ?

(Nothing crypted, no specific acces to my usb stick, my configuration looks the simplest we can imagine).

Best regards

Clément