You will have to use the vmquery -deassignbyid command
instead of bpexpdate. Bpexpdate requires that
Netbackup be able to communicate with the media server
that performed the backup using the tape. Once a media
server is decommissioned incorrectly the only way to
liberate those tapes that were orphaned is to use the
vmquery -deassignbyid command. 

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"A wise man once said 'Wherever you go, there you are'"
      -Mike Brady