SMB connection dropping after period of time

I have this weird problem with our Isilon. Here's the situation.

I have exported the storage via NFS and SMB. I have directories with, lets say, 500GB of data. I'm on a Windows machine with the storage mounted as network drive via AD group policy. I'd start uploading given folder (200GB for example) to Aspera (paid web service for file sharing) and leave it uploading. At given time the transfer will stall, losing connection to the storage and eventually will fail. Tested 4 times and 4 times it happened. Always with data over 100GB in size.

Also tested on a linux machine, accessing the cluster via NFS. Absolutely no problem there. So I think it goes down to samba issue.

Any help will be appreciated!