On the NetBackup master server, do the following when no jobs are running:
Check the following directories for drive entries when no drives are being used:
ls -l /usr/openv/netbackup/db/media/drives
ls -l /usr/openv/netbackup/db/media/tpreq
If you see files in any of the directories you can remove them.
Next, you can reset EMM using the following command:
/usr/openv/netbackup/bin/admincmd/nbrbutil -resetAll
After EMM is reset, start up another backup job and your stuck resources should be available.