NetWare 6.5 SP7, NSS volumes, no TFS.
NWClient 4.91 SP4 + Hotfixes. (Also tested 4.91.0, *.1, *.2, *.3)

For several workstations maybe once a week up to few times per day it
happens, that the volumes "flap" in the view of the client:

E.g. "H:" should point to "FS1_DATA1:". But at some point it suddenly
points not to "DATA1:", but to "SETUP:" or other volumes of that server.

In the Windows Explorer the drive mapping is still presented as
"DATA1 on Server FS1".

When doing a start, run, "\\FS1\DATA1" for *THIS* Workstation it also
in fact points to "\\fs1\SETUP".

It also happens, that two other volumes are involved: F:=fs1/sys:
suddenly points to fs1\edv:, for mapped drive and UNC addressing as
specified above.

When this happend, a windows logout and re-login almost never solves
the problem, a WS-reboot *ALWAYS* solves the issue.

Other Workstations are never affected at the exact same time.

eDir Health check is OK, EDir is one partition. Time is in sync
throughout the just 5 NWServers. No WAN links.

The Server's NIC (Intel Pro 1000 MT Server Adapter) has no errors in
Monitor, nor is there any suspect values for the Server's or the WS'
port at the Cisco 3570 Switches.

Anybody who ever came across such a strange behaviour?

Any suggestions?

Regards, Rudi.