SMB / Oplocking settings should be checked

>Hi,
>
>I have a customer where users are having a problem (intermittently but pretty much every day) with the error reading files (different files (dbf or fpt) at different times.
>
>The IT assures me that the server is fine (it is Windows Server 2008 r2). He says the network if fine. Since the errors happen from different computers I don't think the problem is with one computer/one network card.
>
>What can I ask them to check? Or check myself?
>
>TIA