We have a problem with one of our file servers.

We have a main site with 15 sub-sites.
All users on all sites connect to a server on het main-site.
Sometimes the mapping cannot be made with te following message:
LOGIN-LGNWNT32.DLL-400:A network drive cannot be mapped to a drive that is
designated as a local drive.
When the users Right-Click on the red N and login again the mapping is

When I use CX or RIGHTS on my DOS-BOX, sometimes there is no response.
Sometimes I need to run the command 4 times before I see a response
(Rights are set or the place of CX in the tree)
There has not been any upgrade's, new install's or configuration changes.
This has worked for a few years, never had any problems.
Also, there has not been a large user growth.
Utilization is fine, cannot see any weird things.
If I start a Ping I get 100% response, mostly <1ms.

Server is Netware 6.5SP2
About 1200 user connections.

Can anyone help me with this?

Thanks in advance!