copying large amount of data to usb flash drive slows untill stop

Hi
I got 4 different 64GB usb3 flash drives. I tried copy 23 GB of files (some large as 8GB) in one drag and drop.
I tried these copy wit many formats: I formated the drive as ext4, NTFS and without coping the big files fat32.
The reult was the same:
the copy start fast but then start slowing till its redicusally slow from 200/M/s to steady 50m/s to 9mb/s to less then 1m/s.

I copid these files from an external drive to my laptop. but from my laptop out to the flash it just unworkable. It seems to work better when the governor is on performance but thats just a feeling.
This copy works great on my Desktop computer.

Regards
Roi Illouz