mount/umount causes panic

I have a directory full of ISO files. I have a simple shell script that
loops through the ISO files. Each ISO is mounted, a directory listing is
done, and then it is umounted. Each ISO is in good condition. When I run the
script however the kernel panics after 30 to 50 ISOs (never crashes on the
same ISO twice, seems random). The kernel panic is hollering about
"Attempted to kill init". Why would the mount or umount command causes a
panic? I'm running Red Hat 7.3 and 8.0 with the latest patched. Here is the
shell script:

SLOTLIST=`ls slot*`
for SLOT in $SLOTLIST
do
    echo "Moving $SLOT to reader..."
    mv $SLOT reader01

    echo "Mounting..."
    mount reader01

    ls /mnt/cdsim1/D*
    #sleep 50

    echo "Un-Mounting..."
    umount -d reader01

    echo "Moving $SLOT back..."
    mv reader01 $SLOT

done
~