NDMP backup stalls

We are currently using a netvault backup system in combination with a Netapp filer. To be able for netvault to communicate with the tape library and the tape drives to make the backup ndmpd is used as a deamon. However in some cases those sessions will be hanging. Only in extreme cases. This is what I found in a help document, it can come in handy if you have a problem:

NDMP backup says "Writing to Media" even though it is not writing to media.
Affected NV Version: 7.4.x
OS Version: All
Plugin version: 6.3.x
Application version: N/A

Description:
Several jobs continually say "Writing to Media" even though they are not writing to media. If you look at the logs, it shows a "Channel Error" near the bottom of the log. In "Device Manager" the drive used for these backups says: DRIVE 1 (Locked by Session(Hard).

Solution/Workaround/Procedure:

Most likely the ndmp sessions on the filer have entered a hung state. Issue the following commands at the console prompt of the filer;

ndmpd killall
ndmpd off
ndmpd on
ndmpd status (shows if all strays processes have been eliminated)

This should resolve issue.