you need a custom.sh file-.
for this create a text file and copy this comand .
sed -i s/'shd2:06:wait:\/bin\/umount -a -r -f/shd2:06:wait:\/bin\/umount -a -r/' '/etc/inittab' &
save file as SH extension . name file to custom.sh
on batocera press F1 move this custom.sh file to Share/system .
after moved the file press this key combination.
it will ask for reboot and you get that problem solved .