Xsan 4 and SMB sharing on Windows: issues

Good Morning Xsan Admins.
I recently setup an Xsan 4 Full yosemite 10.10.1 with OS X Server 4.0.3
The MDC1 and 2 are properly configured as DNS and OD master and Replica

Every workstation that regularly mount the Xsan volume, access to the San with an "Edit" users
The resharing in AFP and SMB is done by the MDC servers by a simple local user named "share", always. No special permissions. The simplest of the simplest with R/W to everyone

The network resharing in connected from a Mac works flawlessly in both AFP and SMB. I can mount the Volume, read and write everything without issues.

The network connection from a windows machine is causing me troubles.
I can access the Volume with the user "share", and also map it regularly as network drive.
I can see all the files
I can access and create folders, and also delete folders (if empty)
BUT
I canNOT copy files inside the Xsan volume, nor copy them from the Xsan Volume to the Windows desktop.
When I try to copy a file, the progression bar of the copy on windows appears, showing that he's copying, but always not moving, and generate files of 0kb. I do not receive any error message. It just stays there stuck. This happens in both way, copying into the Xsan volume, or copying from.
No denied access, no errors at all.
No firewall, no antivirus running, tested on Windows 7, 8 and 8.1 and different physical machines

Same result connecting with Admin account 501

The volume has been created twice to test this: tried both with Native Extended Attributes enabled or Disabled. Same problem

Do you have any idea for this issues?

One last thing: If i share a LOCAL folder, outside the Xsan volume (let's say the desktop), i do not have any issues with that folder, and windows works perfectly