Exabyte VXA-2 Packet-Loader and chg-zd-mtx nagging problem

>>From the packet-loader manual the following timing information is available:

Autoloader power-on sequence time (power-on to ready status):

53 seconds when autoloader contains 10 cartridges with bar code labels
105 seconds when autoloader contains 10 cartridges without bar code labels

Cartridge inventory time

average for all 10 cartridges

25 seconds when the cartridges have bar code labels
80 seconds when the cartridges do not have bar code labels

average for an individual cartridge

22 seconds when the cartridge has a bar code label
32 seconds when the cartridge does not have a bar code label

Move complete time

remove a cartridge, return to cell, position a different cell, and load new cartridge

22 seconds

I also followed the instructions in the comments of the /usr/lib/amanda/chg-zd-mtx script and modified the
/etc/amanda/new/changer configuration file to read like this (note overly conservative values to make sure
things work):

firstslot=1
lastslot=10
cleanslot=-1
driveslot=0
havereader=1
autoclean=0
offline_before_unload=1
unloadpause=10
initial_poll_delay=30
poll_drive_ready=10
max_drive_wait=240

My AMANDA nightly crontab entry now looks like this:

/usr/sbin/amdump new && /bin/mt -f /dev/nst1 offline && /usr/sbin/amtape new slot next

When testing this manually from the console, I receive the following error message when running the amtape command:

amtape new slot next
amtape: could not load slot 7: mtx: Request Sense: Long Report=yes

However, after a long wait, it in fact DOES perform this command correctly and has the next tape loaded as it should.

This is my only nagging bug. What is causing this and how can I fix it ?