conclusion:
1. Explanations:
NFS stales occur when a (auto)mounted filesystem (or file) is either
no longer exported, or the machine where it resides is down or
again the filesystem does not exist any more.
Find out which filesystem it is and do a manual umount of it
on the machine where the stale is.
A good explanation about how to debug the problem can be found at
http://www.Sun.COM:80/sunworldonline/swol-10-1995/swol-10-sysadmin.html
2. Work to do:
If the mount is busy, do a fuser -u <mounted-filesystem>
and either exit or kill all the printed processes (use -k to do
it automatically).
Use the the script fhfind from the above location to find out
the i-node.
3. What happened:
The reason for my problems were, that the configuration of our samba servers were such, that both servers on two different machines used the same directory for there lock files with the same lock file names. In this configuration the one server could open the file while the second server (on the exporting machine) could erase it. When this happened the mounting machine detected the STALE NFS FILE HANDLE with the respective file handle.
With the help of the script fhfind from the above location I was able to find the respective file from the file handle information. From this file I could find the software that was missconfigured.