Things get stuck while in sync

[berber]

Hi

I'm syncying large files (hundreds of GB per file) between two external disks.
While the file is in sync, I can't download files using chrome as they seem to download but don't get to the complete stage and just "hang" untill the file sync is over or i stop it.

Simlar problem when trying to save files over FTP to a remote server. File is saved but the process is not done and hangs till i stop the sync.

Any idea why?