Check out this EMC tech bulletin:
esg104075: NetWorker: Potential data loss issue using Path to Tape on NetWorker 7.5 and DL1500/DL3000 firmware version 1.1
esg104075: NetWorker: Potential data loss issue using Path to Tape on NetWorker 7.5 and DL1500/DL3000 firmware version 1.1