tty screen corrupted when sending nano to the background

Hello,

This may be a nano issue, or perhaps this is just something I'll have
to accept while I work in this limited install environment.

I've been trying to reinstall my gentoo system as my RAM went bad and an
unknown number of my binaries/system files were corrupted.
I started gentoo's install cd and start screen. I then run.
mount -o relatime /dev/sda1 /mnt/gentoo
mount -o bind /dev /mnt/gentoo/dev
mount -o bind /sys /mnt/gentoo/sys
mount -t proc none / /mnt/gentoo/proc
screen
env -i HOME=/root TERM=linux chroot /mnt/gentoo bash -l
# The reason I don't use TERM="$TERM" is because the stage3
# tarball does not recognize screen.linux as a valid TERM entry.
# (screen is not in the stage3 tarball so there is not terminfo).
nano
Alt-Z, Ctrl-Z
# Enter cool commands.
fg

The display becomes blank in several places and the mouse pointer rapidly
changes places.
When suspending less this does not happen.

Thanks,
David