Yup, completely normal, unfortunately.  If you want to use both drive, you
can use the DSMLABEL utility and specify both drives:

$ dsmlabel -library=\whatever -drive=\mt3\whatever,element #
-drive=\mt4\whatever,element # -search -barcode -keep
where the whatevers are the unix device names and the element numbers are
where the whatevers are the unix device names and the element numbers are
116 and 117 (I think) for your robot.  This will use both drives to label
tapes.

Kelly Lipp
Storage Solutions Specialists, Inc.
lipp AT storsol DOT com
www.storsol.com
(719) 531-5926