Many thanks for the bug report.
'vtltape' is not keeping enough persistent data between unload -> load to be able to recover from this sequence.
If the robot is involved, the 'barcode' is passed to the drive via the message queue. Performing a 'mt -f xxx offline / load' directly means the 'barcode' is not being passed to the load.
Fixing this shortly.
Cheers
Regards from Australia
Mark Harvey