I was able to boot by connecting to the serial console and pressing 4 after power on to "enter boot command line interface". From there I added the bootarg init=/bin/sh and booted
setenv bootargs init=/bin/sh console=ttyS1,57600n8 ubi.mtd=7 root=ubi0_0 rootfstype=ubifs rootsqimg=squashfs.img rootsqwdir=w rw saveenv
bootm c0040000
If that doesn't work try again but bootm bfd40000 or use the second image per this post
I was able to remove a file or two and then boot normally and log in and delete the second image using delete system image and now has basic function.
Unfortunately I can't restore/upgrade a normal system image:
add system image http://local-server/ER-e50.v1.9.1.4939092.tar
Trying to get upgrade file from http://local-server/downloads/ER-e50.v1.9.1.4939092.tar
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 76.6M 100 76.6M 0 0 25.8M 0 0:00:02 0:00:02 --:--:-- 25.8M
Download suceeded Checking upgrade image...Done Preparing to upgrade...Done Copying upgrade image...Not enough disk space for root file system Do you want to delete old version first? (Yes/No) [Yes]: yes Removing old image...Done Still not enough disk space for root file system Canceling upgrade