i've been having these 'Eject aborted' messages for longer than i can remember, but subsequently running the vmupdate command to re-inventory always works fine. I've never worries about it, i vaguely (and i really mean vaguely) recall this happening since we went to NBU 4.5.
Here's an example. i just moved a tape out to load port and back in, via the exact same way i always do it -
vmchange -res -multi_eject -w -verbose -rn 0 -rt tld -rh nthsunbackup -vh nthsunbackup -ml CH5704
*** Eject volume batch #1 is ready to be removed ***
remove 1 volume(s) from media access port(s) of robot number 0 now
(press to continue)
Slot# MediaID Barcode MAP_Element# Batch Status
31 CH5704 UNKNOWN 1 1 Eject aborted.
vmupdate -rt tld -rn 0 -rh nthsunbackup -vh nthsunbackup -use_barcode_rules -empty_map
Generating list of recommended changes ...
Proposed Change(s) to Update the Volume Configuration
=====================================================
Volume configuration is up-to-date with robot contents.
Rich