Hello,
What version of Networker are you on\OS, can you check your daemon logs 
for any "WISS" errors, it may be possible that your media dB is having 
problems or corrupted.Running nsrim -X and nsrck -L5 may help ( Read up on 
what to expect and when to run this cmds).
If your drive orders is correct and configuration accurate, check the 
timer values, CDI settings.
Under some circumstances running nsrjb -HEvvv may help sort out  jukebox 
confusion. ( No backups or any other networker actively ongoing while 
running this cmds)
HTH

To sign off this list, send email to listserv AT listserv.temple DOT edu and 
type "signoff networker" in the body of the email. Please write to 
networker-request AT listserv.temple DOT edu if you have any problems with this 
list. You can access the archives at 
http://listserv.temple.edu/archives/networker.html or
via RSS at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER