Why do files take a long time to open from a network drive of one of the 2008 R2 servers?

Question

Windows Server

Greetings!
Something I broke my head with this question ... There are 2 file servers 2008 R2 in the domain, network drives are connected on the clients, from server A all files open instantly, and from server B with a delay, this mainly concerns office files (Office 2007). For example, PDF opens quickly from both.
There is a well-known FileValidation problem, but I don’t think it’s about this case, since it opens quickly from one of the servers. The conclusion suggests itself that the problem is somewhere on the server, but where?
_UPD

• To put aside problems with DNS and NetBios - if you go to the ball by IP, the problem remains.
  
• SCS is new and certified.
  
• The disk array is fine.
  
• Disconnected server ESET - does not help
  

Answer 1

Problem solved!
As always, everything lay on the surface, ESET is to blame for everything. I tried turning it off, it did not help, but after I added the path to the exception, everything worked fine.
Thank you all for your participation.

Answer 2

The problem is with office files? What does ping say? Delay time. Does this problem exist on all clients? And if you go directly to the server via RDP and open it from there, is there a problem?